The Frontlines Premade issue has not been fixed.

[Moonlite]

If being freelancer become permanent, achievements must be neutral or else I need have the luck of landing on a good team, plus the luck of landing on my GC side of the arena.

It goes three times harder to achieve <n> victories with my GC.

That is not how wins towards achievements work. The wins are tied to the GC you belong to not the GC you win with. But if you change GCs everything starts over for the new GC. The wins count separately for each GC. Again who you are matched with has ZERO impact towards your win count for achievements. This has never been an issue, ever. How wins are counted is one of the things they got right the first go around.