If you send medicals after submitting your 485 separately, yes, per USCIS, it might delay the process. I don’t know how. USCIS states that it does, though. Maybe, they are having problems with putting all separately-mailed docs together, idk. Maybe it interferes with their setup workflow.
Some medical deficiency notices even say DO NOT MAIL THE DOCUMENTS AT THIS TIME : Mailing the documents before receiving one of the notices referenced may delay your case.
If you are submitting a 485 after VAWA is approved, attaching medicals to it right away might be beneficial. USCIS has mentioned that on their Twitter a month or two ago (it was a general, not VAWA-related statement, obviously). I did not submit my medical 3 years ago with the 485, because I knew it would expire before USCIS had a chance to get to it.