> And also would changing Finn's question to the perfective have any effect on the feeling of the sentence?
No. Both sentences can be switched to perfect/imperfect independently without changing overall meaning.

> ...they surely must be talking about it in the same aspect?
No. Hmmm.... I try to explain it in some way...
Imagine dialogue:
- Ты знаешь про Джона? (Do you know about John?)
- А что он опять натворил? (What did he do again?)
- Он льёт азот в воду! (He pours nitrogen into the water!)
Are you confused with "tense missprediction" in this example? I am interested...