Most "absolute" statements about what more or less timing does are incorrect because of the number of variables involved. Some engines need very little advance for MBT and knock is not much of an issue.
Speculating about why the timing spec is the same for 3 models with 7.5, 8 and 8.5 compression engines is a good example. More info is needed.
AFAIK, the prior versions all had different octane fuel spec's and these models were all spec'd for 91 RON unleaded, a drop of 7 octane numbers from the 9.8 S. The factory did point out that performance numbers all improved, but after the political events of the embargo, consumption was the number that mattered. So they took a different path, raised compression to improve consumption, and detuned the timing to prevent damage. Advertising for the later SC and Carrera focused on performance increases with consumption decreases. The distributor spec is 32-38 max, which shows the slop in a mechanical distributor even when new.
Normally a larger bore would require more advance, but after 1972, it was a politics not performance that dictated timing specs.