If you tell search everything to index \\wsl.localhost\ And have the option attempt to monitor changes on, MSRDC will keep stealing the focus from the foreground application.
If you disable monitor changes, everything works great.
Thanks to "Spongeloaf" who figured this out! https://github.com/microsoft/wslg/issue ... 1896250914
I'm mostly sharing it here if anyone else runs into the issue.