True, but when was the last time a POTUS termed out or declined to run for another term, and their VP wasn’t the nominee (if they ran)?
As far back as I can remember:
LBJ → Hubert Humphrey VP then won the nomination
Nixon resigned, Ford was defeated, Carter was defeated
Reagan termed out, GHWB was VP and got the nomination
GHWB was then defeated by Clinton
Clinton termed out, and VP Gore got the nomination
Bush termed out, Cheney didn’t run.
Obama termed out, Biden declined to run but probably would have got the nomination over Hillary.