Do they, though? Let’s compare.
M60 RISE (P): Worse armor, worse mobility, no LRF, worse round (Currently, the patch broke it and it may be fixed in the future). Benefits: Better gun handling, more gun depression.
T-62: Worse armor, slightly worse mobility, no LRF, worse reload. Benefits: Better round, one extra degree of gun depression
Obj 435: Haven’t played it, can’t discuss it with confidence.
Chieftains: Worse armor, worse mobility (Cripplingly so in the Mk III’s case), worse round, no roof mounted .50 cal, no LRF. Benefits: Slightly better gun handling and depression.
AMX-30 B2 and BRENUS: No armor, no stabilizer. Benefits: Faster, better round, thermals, better gun handling and depression. Bit of an apples to oranges comparison, the lack of a stabilizer is more crippling than the advantages they have over the AMs IMO.
T-55M: Much worse armor, worse mobility. Benefits: Slightly better round.
Strv 104: Worse armor, much worse mobility, no .50. Benefits: better round, better gun handling and depression.
Outside of the apples to oranges comparisions, it does seem to me that the AMs are substantially better than most other 8.7s. It’s hard to imagine a situation where I’d rather be in a Chieftain or a T-62 over either AMs.
Is that enough for them to go up to 9.0? Probably not unless we see more decompression that moves a lot of 9.0 up further. They are notably weaker than several notable 9.0s. But pretending the 8.7 MBTs are well balanced in comparison to each other seems rather disingenuous.