Mercurial's push refers to wrong default url

Project A (a subdir project) contains another project B. In filesystem, project A and B are two folders in the same folder (i.e. B is not contained in A in the filesystem). Both projects have a mercurial repo, with the default push url be x.com/a and x.com/b. The behavior is inconsistent.

When a file in B is opened, the commit behavior is normal, it refers to the repo in B, but the push behavior (and pull) has the wrong default push url, which is x.com/a, while it should x.com/b.
And the push result is "repository is unrelated" since it executed push in B but with A's url, x.com/a.