Multiple inputs works fine with gpu pass through, but regularly switching monitor inputs is honestly a pain depending on your monitor. Its like a 10 second process for my monitor.
Also people running a setup like this are using the Linux host as their main desktop. If you only have one monitor and are switching inputs you lose your whole workflow on Linux host when using the vm. It’s better with dual monitors but I’d still prefer looking glass.
The switching process can be disrupting depending on how it works, I agree. But even so far as to include grabbing a spare monitor "you never actually look at" or spoofing one? For that, I admit I can't see why just using one of the inputs on the monitor you already have isn't an option.
Unless of course the monitor doesn't have additional inputs (but it was never specified the hypothetical monitor is ancient) or they are all already used (again wasn't specified).
Also people running a setup like this are using the Linux host as their main desktop. If you only have one monitor and are switching inputs you lose your whole workflow on Linux host when using the vm. It’s better with dual monitors but I’d still prefer looking glass.