Take a look at this terms from here https://www.revolut.com/legal/cryptocurrency-terms
Ooft. This is wild. Check out some of the things they say:Quote
We will legally own any cryptocurrency we buy for you.
At least they are being honest about not your keys, not your bitcoin. 
Quote
Unfortunately, for reasons beyond our control, a fork may cause a cryptocurrency we hold for you to be split into two cryptocurrencies. If this happens, the following may apply, as we see fit:
youll get a balance in the one of those two cryptocurrencies that our partnered exchanges decide to support as the main cryptocurrency; and/or
you wont necessarily get any or all of the two new cryptocurrencies (for example, if our partnered exchanges decide not to support those cryptocurrencies).
Emphasis mine. So either they keep the forked coins or they keep ALL your coins? Pretty much legalized theft.youll get a balance in the one of those two cryptocurrencies that our partnered exchanges decide to support as the main cryptocurrency; and/or
you wont necessarily get any or all of the two new cryptocurrencies (for example, if our partnered exchanges decide not to support those cryptocurrencies).
Why would anyone use this? Not only do you not get to own bitcoin, you aren't even allowed to transfer or spend your bitcoin. They own it, and may even decide to just keep it all if they want. This is even worse than a web wallet, and I didn't think that was possible. AND you have to pay fees for this.
They also make zero mention of how your bitcoin is stored other than on a "virtual account". Very concerning.
I'm not familiar with this service, but I'd be avoiding it at all costs.