I might have neglected that ...

I agree with you, and I didn't deny that Present participle with perfect tense can be used as subject, and it should.
Just that I failed to make a sentense to use "Having studied ..." as a subject. However, present participle with perfect tense or (passive voice) should be able to be used as Subject.

Here's a sentense below and I think it should be correct both grammatically and semantically:
Having been able to ride a bicycle doesn't necessarily mean you can ride a pedicab (a tricycle).

(I remembered the first time I rode a pedicab to help my friend moving furnitures, the pedicab goes directly to the wall although I had tilted my body hard for the right direction (like riding a bicycle), it just didn't work).