I read this presentation (April 2022) again. There is an ironic twist. There was a time not long ago that people are saying that CZ-7 series will only have the 2 stage variant for cargo launch to the space station while most other jobs are done by CZ-8 series. It seems that number 8 will be the short-lived one as the slide says that both 6 and 7 will be replaced by 7B,C,D.
One thing to note is that CZ-7C is essentially CZ-8 with elongated 1st stage, CZ-7D is CZ-8A elongated, plus the new 2nd stage with one YF-75E replacing two YF-75.
As I always say 6,7 and 8 are all 7 from the beginning, and maybe will end up in 7 in the end. It is just a number or letter, no big deal. But Long Lehao does do a good job to keep us confused.