Any truth to this 396/402 update?

[Kurt S]

To go back to this, I suspected it was related to emissions too. But I've never found any 1970 rule change that being over 400 cu in would help. And .030 wouldn't affect emissions enough either.

But for some reason, they made the change. And it got really confusing cause they called it a 396, but it was a 402. But all the service docs called it a 400 - and there was also the SB 400. Reading service docs can be like a replay of 'who's on first...'