You ask to discuss about the block data.
Does Bitcoin blockchain "know" about BCH splitting off? I don't think so. According to bitcoin's blockchain BCH doesn't exist.
That BIP activation and the split is recorded probably on BCH chain, which doesn't matter in this discussion, since we talk about bitcoin, not altcoins.
So, I may be wrong, since I don't know the things that good, but imho you are also getting into the discussion things that should not be there.
It's all about how one looks at the things.
the bitcoin code and the bips refer to a block number where a split would happen to start the segwit activation process. and guess what magic blockheight BCH started at...
.. ill leave you to answer that when you have a lightbulb moment.