I know they were removed from the game. That's why I didn't assign them to specific mechs, but made them a random modifier. Not all A mechs have quirk B, just some mechs that you find in the store or salvage on the battlefield may have, for example, the “improved targeting computer” quirk.
This is done to ensure there is at least some progression. Alpha Strike is a very balanced game, and when you get a more powerful mech, it costs a lot more points, so you don't get the same advantages as in a typical RPG when you get a magic sword +2. Having quirks can help in this regard, at least to some extent.