I have completed the battleground season 5 pass 40 levels, but I just realized I still miss two items which should be obtained in the pass. Thorim’s thunder (rare and epic) I have got legendary to prove I have completed 40 level’s pass.
I’m not sure if this is a bug. The rare and epic version of that strike are shown as missing in my collection as well but I think once you earn the legendary version only this one is available in the collection.
If you check the description of rare and epic version, it states that is available after purchasing s5 battlepass, and I am sure it is a reward from s5 pass