this is a repro for an issue reported by a user on mac (8.2.23339.13002, 2023-12-05), which I have confirmed on mac (8.1.23325.13002, 2023-11-21), but not on windows (8.1.23325.13001, 2023-11-21)
create a Custom material
assign a 2D Checker to Color
right-click the material > Copy
right-click the materials panel > Paste
the child textures of the two Custom materials will not be marked as instances, will not have the “Remove Instancing” context menu item lit up, but will otherwise behave as instances, with changes to one affecting the other, and with both being selected in the list, when either is selected
looks like that is it – I think I have never even opened the textures panel on mac, so indeed that was checked, and I confirm that unchecking it gets rid of this instance-like behavior
thanks for the confirmation. I’ve asked why that checkbox is there in the first place. To me it looks redundant, since we already have a way to make a true instance.