Krdp shares existing remote session like VNC, rather than start a separate session like RDP

If you read the announcement from one of KRDP developers, here - KRdp in Plasma 6.1 | Quantum Productions - it goes in a bit about why actual remote login is a much bigger problem.

There’s a bit more discussion about it in this thread: Plasma 6.1, RDP, start server via terminal?

TL;DR - maybe in the future, the far future.