I have a great question.

How does launch control work on a subaru and doesn't matter which gen or engine it is if its awd you can't have a rev limiter because their is a no non driven wheels.

Your question is slightly confusing and also I think launch control is a bit mis understood.

launch control is a feature mainly driven by set input to limit the end for launching whether it be from a dig(stop) or rolling. It will slightly differ depending on tuning solution and also how you choose trigger it, most launch controls use wheel speed sensors or vehicle speed sensors if opted along with rpm signal and other sensor feedback information to operate no matter if 2wd or awd, every system can be unique depending on tuners skill level and application.

Agreed, the chaps question isn't that clear. Perhaps if he would clarify?

My 5 cents worth, if I understand his point, and change may be due... Pretty much the reverse of ABS.

Don't know about Subaru, but a basic form of AWD traction control will monitor the wheel speeds and, if one is rotating significantly more than the others it will trigger a torque reduction. If all tyres lose traction evenly, which is most unlikely, then I would expect it not to trigger.

More advanced systems may use accelerometers as well, so if the increase in wheel speed isn't matched by actual acceleration, it could reduce torque until they match.