I think there is a psychological aspect here as well due to confirmation bias — all caches will be wiped during an update so even due to that the first few hour

I think there is a psychological aspect here as well due to confirmation bias — all caches will be wiped during an update so even due to that the first few hours/days may be slightly slower. If people make this assumption they can later easily find evidence for that (or its negative as well, if they would try to look for that)