Me and others noticed this bug as early as with the first SU9 beta
https://forums.flightsimulator.com/t/performance-at-ksfo-massively-down-in-su9beta/508831
on April, 3rd (!), at which time it was not yet known it’s caused by the PG cities. I tested several places, here’s an extreme result besides KSFO: Miami Opa-locka KOPF on ground, Community folder empty except Shift+Z mod, 22 fps with PG Cities, 42 fps without PG cities (both on pancake screen). That’s a factor of 2!
This is a glaring bug. Maybe not anyone is hit by it but I am tracing several fora (not only this one) for this bug and there has been an overwhelming number of confirmations already. And there are certainly a number of users not following any fora or even new to MSFS just finding for themselves MSFS has “terrible performance” - which it doesn’t have as such, it just has a temporary bug.
Which, btw., has been even confirmed by MS/Asobo themselves as my thread - and a number of related ones - are marked “bug-logged”.
Unfortunately, there has been no sign since if this can/will be solved with SU10.