I think the argument is supposed to be about ROI but it didn't really drive the point home: They don't want to invest in integrating their product in Gitlab, b

I think the argument is supposed to be about ROI but it didn't really drive the point home: They don't want to invest in integrating their product in Gitlab, because it's 1/4 the size of Github and they see trends pointing to a Github resurgence. If you have limited resources to build integrations then sure, I guess?