If that were true that it wouldn’t be just a side note because it would render the whole Bitwarden product useless. It’d pretty much mean that they are not encrypting passwords at all, so even worse than infamous LastPass. But as the other comment pointed out, it’s pretty much not like that.
In my setup I still use reverse proxy even though all of my services are inside a VPN. IMO it is just more convenient to have services accesible as subdomains or subdirectory than as different ports.