To clarify, was this the sequence of events?

1) Sign in to both profiles
2) switch back to primary profile
3) start crostini app
4) immediately switch to secondary profile (before app has started, during spinner?)

then the app window is appearing in the secondary profile?

I did the following:

Start weston-terminal with corp profile
Add personal profile
See weston-terminal on personal profile "desktop"

How do you install wlterm?

sudo apt-get install wlterm 

doesn't find it for me.

weston-terminal comes grom the "weston" package. that should work for testing or you can build wlterm from https://cgit.freedesktop.org/~dvdhrm/wlterm

I was able to repro this. 

sudo apt-get install weston

$ weston

There is no launcher icon, nor is there a shelf icon. I suspect this doesn't have a .desktop file?

The lack of shelf icon (not even the penguin) probably means sommelier isn't handling the window in the way that Tim's shelf code expects.

This app doesn't set application_id or startup_id on the surface. Chrome failed to identify it as a window from the Linux container.
To make it work, I think sommelier can set a property on the surface to indicate it's a Crostini app window. Perhaps this can be done together with multiple container support.

https://bugs.chromium.org/p/chromium/issues/detail?id=846213#c3

As proposed in the above comment from another bug, crosvm pid (vm_concierge?) can be used to reliably identify the Crostini apps. This is especially needed for this kind of edge case apps.

wlterm is not heavily used, punting to M71.