It's not clear to me, is what just happened even possible on main net?
No, because there's no way anybody would risk real money with SegWit2X clown code.
The '6000 blocks mined in day' talking point distraction is obfuscating the real problem that the code then got stuck when the (accelerated) HF happened ... you know like the piece of the code that whole client is in existence because ... it's raison d'etre is broken.
They should be thanking whoever accelerated the '6000 blocks in one day' for showing them their fundamental brokenness bugs (how fucked they are) ... instead we get BS talking points about ASICs on testnet, wah-wah, who knew?