I would say yes and no, but yes the clone command can do it. But branching and CI get a bit more complicated. Pushing and reviewing changes gets more complicated to get the overview. If the functionality and especially the release cycle is different the submodules still have great values. As always your product and repo structure is a mix of different considerations and always a compromise. I think the additions in git the last years have made the previous really bad pain points with bigger repos less annoying. So that I now see more situations it works well.

I always recommend keeping all testing in the same repo as the code that affects the tests. It keeps tracking changes in functionality easier, needing to coordinate commits, merging, and branches in more than one repo is a bigger cognitive load.