Because the AF8/A8F is about to pull its curtain , preparing for the upcoming A9G and A8G .

Yes , solely for the price . Especially since all OLED tvs are relatively identical with each others , just get whichever that is the cheapest you can find .
( I am strictly talking about the Panasonic , LG , Sony and Philips / TP Vision , excluding the Chinese OLED TVs  )

I have a fairly long list of issues with AF8 but if someone can find a new 65" OLED for $7999 I am not going to tell them NO .

Unfortunately that is still happening , Sony's dimming algorithm is more aggressive than other brands .
Screen dimming serves as part of the protective measurement against Burn-In so there is nothing you can do about it , not on Sony's TV at least .
A while ago , Sony has released patches to mitigate the issue but it wasn't very effective .
To be fair , these dimming effects shouldn't be very obvious unless you are watching high APL / very bright HDR scene.
If you are in a dim room , the TV brightness should be calibrated to around 100-120 cd/m2 anyway .  ( brightness settings of around 9~10 on Sony's OLED and 33-40 on LG's OLED )
In that case you will not notice much of a brightness shifts when the TV is playing non-hdr content , be it ABL or static logo dimming .

Dimming effects are also less noticeable on the newer AF9 and AG9 models because they are not as bright as AF8 .