This article has more detail, because Apple spoke with iPhone in Canada: "Apple also gave some further technical information on the situation to iPhone in Canada."
"Apple explained to iPhone in Canada it has already fixed this performance issue through a server-side update, that will now allow macOS to cache Developer ID OCSP checks for a longer period."
Being discussed here: https://news.ycombinator.com/item?id=25107679
This article has more detail, because Apple spoke with iPhone in Canada: "Apple also gave some further technical information on the situation to iPhone in Canada."
They comment on the OCSP issue but fail to comment on the Apple application exemption from filtering in Big Sur?
https://twitter.com/patrickwardle/status/1327726496203476992
"Apple explained to iPhone in Canada it has already fixed this performance issue through a server-side update, that will now allow macOS to cache Developer ID OCSP checks for a longer period."
I discovered this and blogged about it on Friday: https://lapcatsoftware.com/articles/ocsp.html