Not a VPN, TOR just runs as a SOCKS proxy on whatever device you're using[0]. Replacing the actual network stack at OS level was considered but iirc was decided against because it would require admin permissions.
The TOR browser and Brave do the exact same thing, it's just that the TOR browser is configured to not store anything and to make sure it's fingerprint to other sites is as generic as possible (this is also why TOR warns you about changing window size, it un-generalizes that fingerprint). Both ultimately are conveniences because messing with SOCKS proxy settings is rather unfriendly for most users.
If you use a Linux distro, I'd recommend checking out torsocks[1], it's a shared library + a shell script that lets you "onion-ify" any application pretty easily.
[0]: This also means you can connect basically every mainstream browser to TOR if you know the port the SOCKS proxy is running on.
It would certainly make sense from a marketing perspective to claim it's using tor, and then have a tor-proxy service (think onion.cab) use tor for hidden services and also attempt to use tor for clearnet traffic but fail back to regular proxy if it fails.
If it were directly using tor then I'd have to agree that most people wouldn't use it. Only those that are technical enough to understand what's going on and the security aspects. But they wouldn't be using Brave for the Tor functionality, they'd be using Tor Browser.
