QtCreator fails to locate .pro files that are named differently than the parent dir

Bug: if a qmake subproject has a .pro file named differently than its parent dir, QtCreator can't find such .pro file.
Example: libs/mylib0/mylib.pro can't be found by QtCreator even though it is specified in root pro file (mylib.file = libs/mylib0/mylib.pro)

Reason: QtCreator always derives the name of the .pro file from the parent dir's name. I have seen that in QtCreator's source code in the file src\plugins\qmakeprojectmanager\qmakeparsernodes.cpp: QmakeProFile::subDirsPaths method (lines 1919 and 1920 for v17.0.0)

I've attached a project that can be used as an example (it is not mine, but I've modified it). QMake builds it successfully, but QtCreator fails to locate libs/mylib0/mylib.pro

The question: is that a bug or normal behavior?