How can you make WES7 on a D90D get a user CAL instead of a device CAL on RDS?

We have a couple of Windows 2012R2 RDS installations using D90D clients. We also have a licensing server with both User and Device CALs installed. The RDS pool is set up to use User CALs.  However, I haven't been able to get the clients to use the User CALs--they are all asking for and getting Device CALs. User CALs are being given out, but I think that they are being given out for RemoteApp sessions from the virtual desktops. If we run out of Device CALs, which we do occasionally, the clients won't take a User CAL--they just give an error saying that they couldn't get a license. Is there some trick to this, or does it just something that doesn't or isn't supposed to work? I have tested this with the thin clients both joined to the domain and not joined.

Thanks for any ideas.

Matt