I both agree, and disagree. The weird thing is that I treat this situation totally different between modelers and amps. If I show up and get told “use this amp” I say cool, plug a board in, turn some knobs, and rock on.
With a modeler, I just don’t. It’s too fiddly to try to get a modeler dialed in unless it’s just a basic dry clean sound that I can plug a board into like I would a back line amp. I plug my own rig in and go. Generally at a gig that’s running this way the monitoring situation is baked in too, so you can set your own level just getting the monitoring level right. The gig modeler was dialed in to someone else’s guitars and hands, it’s going to sound better off my own rig. I haven’t encountered anyone that couldn’t quickly understand that and be open to trying my rig. This assumes it’s a full rig modeling setup (dirt, compression, effects, etc). If it’s just doing a basic clean tone I can plug a board in and be off to the races, who cares.
This has come up like twice for me, usually the gigs that I’ve seen have direct solutions there are just accounting for guitarists that might show up and not have a silent stage option of their own. I have only seen one or two try to say that everyone needs to plug into the gig rig.
Another thought, some pros decide what they are and are not willing to do for a given gig and then stick to their guns. Dealing with whatever situation presents itself is a choice. You might choose to do it just to prove you can, but you don’t have to. Unless it pays good and you’re starving, then plug into whatever and keep your mouth shut lol.
D