Bad example, Apple's market share is tiny anywhere besides the US.
And this isn't a new thing. They partnered with an established vpn provider. Horizontal scaling won't be an issue there.
There is really no reason, but I don't really care either
And there is really no reason to not go to the actual provider. Same price and you can use it on all platforms. They even provider a wireguard backend.
https://mullvad.net/en/help/pricing-discounts/