You can assume that anything related to the fluff or lore about the scenario hasn't changed between editions, unless said so otherwise.
There are texts from Shadowrun 2nd edition that are still valid to this day, such as the description of the astral planes and their inhabitants.
If the books would simply repeat everything between editions, they would be heavy(er) tomes.
We do know that True Dragons cannot hide their astral aura, even if they are in an humanoid form, so it's safe to assume that Drakes also have a visible dragon-like aura in the astral, just like in prior editions, unless they are using the Mask spell (which is a mana spell and should work on the astral).
If this helps, this is the text about their dracoforms in 4ed's runners companion:
A drake’s defining ability is to take on the form of a small
dragon, called their dracoform or drake form. While in this form
(and only in this form), the drake gains the following powers: Dual
Natured, Elemental Attack, Enhanced Senses (Hearing, Low-
Light Vision, Smell, Thermographic Sense), Hardened Armor 4,
Mystic Armor 4, and Natural Weapon.
As dual natured beings in dracoform, characters can use their
Physical attributes and Unarmed Combat skills in conjunction with
their Natural Weapon attacks on both the astral and physical planes.
The dracoform of most drakes is that of a small Western
dragon, but players can choose for their drakes to be of any of the
known types of dracoforms (Dracoforms, p.295, SR4). Each form
has slightly different traits and modifiers, some of which can be
advantageous and others less so.
I bolded Dual Natured, which is what made them active on the astral plane while in their Dracoform. The text enforces that by saying they are dual-natured beings.
Please note that this means they are only visible in the astral while in their dracoform, while they are in their humanoid form, they are not dual natured.