It's not the tool, it's bad developer practices. See my other comment on multiple people editing the same interdependent constraints. Never a good idea, even in obj-c or swift code.

Complaints happen; it doesn't mean the complainers are using the tool correctly.

But it does raise a possibility: Maybe the Xcode team could make it easier for a developer to do something along the lines of checking out a single scene to work on, at least putting other developers on notice that they will be risking merge issues if they work on the same scene.

Normally issues can be avoided by just coordinating work such that people aren't editing the same code at the same time. This goes for XIB or storyboard "code" too. Yes maybe Xcode could do something, but that something would probably address developer behavior more than it would address merging per se.