He did not say stacked. He said BSI. While all stacked sensors are BSI, not all BSI sensors are stacked. [Edit: I stand corrected and somehow missed that he wrote stacked. That does make it even more laughable though, the R7ii is not getting a stacked sensor.]
It is EXTREMELY unlikely that the R7ii will get a stacked sensor. In fact I doubt it will be BSI either as Canon didn't put BSI into the R6iii.
The R6iii was "rumored" to get a fully stacked sensor, lots of discussion about it getting the R3 sensor, yadda yadda. Even the R6ii early rumors were of stacked sensors.
Personally I think Canon will stuff another low-tech FSI sensor into the R7ii and just bump the resolution. Same thing they did with the R6iii. I'd like to be wrong, but I doubt that I will be.