My fear is that Apple will now make the design decision to make these services more unreliable if blocked. Like I experienced, others too have noticed similar behaviour:

> It’s worth noting that Big Sur and its predecessors are built to assume that they can talk to Apple at any time, but when we don’t allow it, a few unwanted side effects pop up. For example, the keyboard sometimes takes longer to wake up from sleep mode. Or, in certain situations, the Mullvad app takes longer to detect that the computer is online.

- https://mullvad.net/en/blog/2020/11/16/big-no-big-sur-mullva...

(Ofcourse, as a developer, I can sympathize with the Apple developers - when you design a product to use the internet, you don't really think hard about all kinds of use cases where internet access is deliberately denied).