The DVI KVMs I've been using for years have the property that they make the computer(s) that one is switched away from think that the monitor is still connected. This is, in general, quite useful; in particular, if one attaches a laptop to the KVM with the intent of using the laptop's display alongside the monitor connected to the KVM, windows will not reorient themselves when switching away from the laptop.
From what I can tell from researching DisplayPort KVMs, this property (which I have come to consider one of the main things that a KVM is supposed to do, rather than being a simple switch) seems at least uncommon and perhaps entirely absent from DisplayPort KVMs.
Is there something about DisplayPort as a connectivity standard that has invited this regression? Are there DisplayPort KVMs on the market that will emulate the presence of a monitor?