A creature can gain weapon, armor, and shield proficiencies from its type even if it also advances by class level
Each creature type, when appropriate, makes mention of proficiencies gained due to that type. For example, the type fey says that a fey is
- Proficient with all simple weapons and any weapons mentioned in its entry.
and that a fey is
- Proficient with whatever type of armor (light, medium, or heavy) that it is described as wearing, as well as all lighter types. Fey not indicated as wearing armor are not proficient with armor. Fey are proficient with shields if they are proficient with any form of armor.
A satyr, then, is proficient with the shortbow and doesn't lose these type-gained proficiencies upon advancing in class levels, instead usually gaining additional proficiencies from those class levels.
The humanoid type is a little different
A creature with the type humanoid like a dwarf has humanoid traits, including the following:
- Proficient with all simple weapons, or by character class.
- Proficient with whatever type of armor (light, medium, or heavy) it is described as wearing, or by character class. If a humanoid does not have a class and wears armor, it is proficient with that type of armor and all lighter types. Humanoids not indicated as wearing armor are not proficient with armor. Humanoids are proficient with shields if they are proficient with any form of armor.
Emphasis mine. But creatures with the type humanoid with 1 Hit Die like dwarves
exchange the features of their humanoid Hit Die for the class features of a PC or NPC class. Humanoids of this sort are presented as 1st-level warriors, which means that they have average combat ability and poor saving throws.
So such 1 Hit Die creatures will almost always gain proficiencies by character class instead of by creature type, while, instead, for example, a typical bugbear has simple weapon, light armor, shield proficiencies from its type because it has more than 1 racial Hit Dice.