Assume we have two extensions A and B, where A has migrations that depend on migrations in B.
If we now install extension A, while B is present, but not installed, the necessary migrations from B will also be installed.
If we then uninstall A again and delete the data, the migrations from B will not be removed, leaving unneccessary data in the database. At the same time, even though parts of B are now installed, the Link "delete Data" does not show up for B. This is also not the case while A is still activated.
I would expect either the removal of the data from B as well when A is removed since I never installed B, or, which is probably safer to do, to show the link "remove data" for B, once A is removed.
I have created two small demo extensions depending on each other which demonstrate this behavior. The extension "thisdepends" has migrations which depend on migrations in "alldependsonthis".