read the fight again...
Byakuya can't even harm pre-evolution Gerard with his bankai.
Byakuya and Toshiro planned it out VERY SPECIFICALLY:
- Toshiro freezes him and weakens him
- Byakuya crushes and kills him
What they did is exactly this. When Gerard was cut up by Byakuya, you can literally see his insides were frozen too, and there's no blood or anything like that. He obviously can't do that to Gerard normally, if he can't even knick his skin while in regular bankai. He's still a base Aizen victim, and nothing in the new anime will change that.