I honestly can't say right now. All of our VDI desktops have UEM installed. I'll have to set up a desktop pool without UEM and test.
No worries, just wanted to check.
So I removed UEM and deployed to a test pool. When I log into that pool the USB devices show up immediately (and I mean immediately, like less than a second). So this is definitely a UEM and Horizon View Agent issue. Basically if you have UEM 9.13.0 and Horizon View Agent 7.4.0 the Horizon Smart policies for USB redirection fail at first login if you have any kind of delay in login like appstacks.
Oh I also added the HKLM\Software\VMware, Inc.\VMware VDM\Agent\USB\UemFlags set to 1 registry value with Horizon View agent 7.4.0 which it doesn't do anything. As far as I can tell it is just ignoring those any registry entries for that key.