PRD clearly states Sorcerer :
Whenever you cast a spell that deals energy damage, you can change the
type of damage to match the type of your bloodline. This also changes
the spell's type to match the type of your bloodline.
Burning Hands is no longer going to set something on fire as it's spraying acid- there is no longer any element of fire involved- it's been changed to Acid Spray.
Even if PRD didn't come spell it out - it also wouldn't be in the spirit of the game to have burning hands spray flaming acid- and NOT do fire damage- even if it was somehow reduced to a secondary effect. The statement "The sorcerer’s elemental bloodline literally does nothing but swap the damage type of the spell; all other effects remain the same." is both literally and figuratively contradicted by RAW:
The power of the elements resides in you, and at times you can hardly
control its fury. This influence comes from an elemental outsider in
your family history or a time when you or your relatives were exposed
to a powerful elemental force.
The point of the Elemental sorcerer is that the elementals are a part of your very being so the idea of an earth elemental (energy type acid) that also shoots fire (a different element type) doesn't make sense.
Its also clear that there is confusion about what a Descriptor entry is: Here is the definition from the PRD:
Appearing on the same line as the school and subschool, when
applicable, is a descriptor that further categorizes the spell in some
way. Some spells have more than one descriptor.
The descriptors are acid, air, chaotic, cold, darkness, death, earth,
electricity, evil, fear, fire, force, good, language-dependent,
lawful, light, mind-affecting, sonic, and water.
Most of these descriptors have no game effect by themselves, but they
govern how the spell interacts with other spells, with special
abilities, with unusual creatures, with alignment, and so on.
A language-dependent spell uses intelligible language as a medium for
communication. If the target cannot understand or cannot hear what the
caster of a language-dependent spell says, the spell fails.
A mind-affecting spell works only against creatures with an
Intelligence score of 1 or higher.
Lets look at the other important detail - Description:
The description is the meat of the spell, and what you put here is the
most important information of all....People who read your spell description may not
know your intent, and using flavorful language can trick readers into thinking a spell > should have additional effects not explicitly spelled out in the description.
Both from Designing Spells. The point of the descriptor is not some meaningless check vs damage type resistance entry, but actually how the spell interacts with both other spells and the environment. It "describes" the type of force/energy type used.
Lets look at the description of the Elemental bloodline where Burning Hands is SPECIFICALLY called out
These spells always deal a type of damage determined by your element.
In addition, the subtype of these spells changes to match the energy
type of your element
But uh-oh even though Burning Hands is in the list of specifically changed spells it uses the word subtype instead of descriptor - and since spells have no such thing as a subtype it's clearly not really meant to apply....
the subtype is meant to infer the meaning that both the descriptor and possibly description are supposed to change- when the caster chooses the secondary energy type. Note that with burning hands specifically - you don't get a choice, unless you are a fire element you do not get fire as the energy type. There is something else missing here. It doesn't say "descriptor" it says "energy type" - something else a spell doesn't have. So again either you decide that the core rulebook is just plain wrong, or you decide that they probably meant something broader than just descriptor since that fits in with what the character is supposed to be (elemental in nature).
Lets look at the description of Burning hands:
A cone of searing flame shoots from your fingertips. Any creature in
the area of the flames takes 1d4 points of fire damage per caster
level (maximum 5d4). Flammable materials burn if the flames touch
them. A character can extinguish burning items as a full-round action.
So if we don't change the description (which would then have to override the class description) yup you get to spray fire that happens to deliver acid damage (even though the class specifically calls that out- you have to ignore that) and it also means that though you have acid damage you get NO acid effect from spraying the acid "fire". that's neither the intent or any sort of reasonable interpretation of the rules IMHO. Additionally the description presumes that FIRE is going to be created. Being 20 some odd years old, this isn't an unreasonable assumption but the PRD addressed this in the description of sorcerer.
As an aside there no requirement in the rules to turn off your brain. Pathfinder and DnD in general isn't meant to be advanced squad leader, so sometimes you are going to have to make allowances for older rules to combine with newer ones. In general these can be resolved using common sense and specified intent in the guides (which is usually very explicit)