I tried the same exercise on ITK 5.1+ and was able to have a successful compilation. I had to downgrade to ITK 4.13 and the same work doesn’t compile because of linking error. I’m wondering if there’s any difference between ITK 5.1+ and ITK 4.13 that I could have missed out.
I created a ticket concerning this issue on github : Creating a module group with custom modules not compiling for ITK 4.13 · Issue #2334 · InsightSoftwareConsortium/ITK · GitHub