Just because something happens on April 1st doesn't mean it's a joke. Regular business keeps happening, and you need your customers to be able to tell the difference.
If the customers who can’t tell the difference leave and twice as many new ones join, you’re winning.
I’m happy with Mullvad, but I’m more likely to use or recommend Windscribe in future because they do stuff like this (even though I think most April Fools stuff is a bit tired and it's generally overdone, I much prefer companies to have a personality, be quirky, etc. — easy to like is hard to love).
Quite a few years ago (around 2010), gog.com ran an April Fool's joke claiming they were shutting down. They went all-out for it, including blocking anyone from downloading their paid-for games for the day. Unsurprisingly, people were upset, and I saw more than one person vow never to buy from them again. I always wondered how many customers they lost from that stunt vs. how many they gained.