I am quite aware of who Thrawn is, thank you very much for that charming bit of condescension. However, Thrawn is very much in current canon. He was legends. Then, they brought him back. Now, he's canon.
Mara is very much not canon.
Many of the things they bring into new canon from Legends have versions, oftentimes very different. Given Thrawn is unlocked using Phoenix squad, it's safe to conclude they're drawing from the new canon version, and more specifically his Star Wars: Rebels appearance, not Heir to the Empire.
The only characters not in current canon right now in this game are from KOTOR, and arguably some of the generics.