I think that parent means also things like CI, release repository, PR review, etc.
These are not easily portable, but honestly is because of this lock-in that I prefer to use separate/independent tools. For my open source project [0], I am putting things on github and it is the link that give to most people, but in reality is just a mirror to the gitlab repository[1], which I use for CI and static page hosting, and the "project management" is done on Taiga [2]
[0]: https://github.com/mushroomlabs/hub20
[1]: https://gitlab.com/mushroomlabs/hub20/hub20
[2]: https://tree.taiga.io/project/lullis-mushroomlabshub20