Maybe it’s just me but I’m consistently finding this UI confusing. The two cases where I see it and I’m confused are Copy, pasting a block and editing a linked 3dm (you return to this UI). I guess the language is funny? Is “Model” supposed to mean the pasted, new model? or the model that’s being merged with the live model, “file”? Yes I understand it now but this was my confusion.
This is how I think of it…
"This action creates a block name conflict for “Houses.3dm”. Which block do you want to use?