[14v6]

If it was in for service that didn't involve pulling the cover how could they possibly see it? I would have hit it with brake cleaner and wait a month or so to see if the leak was active before replacing a main seal.

Main seal leak involves a lot of disassembly. It may come back with new noises. Good luck with the repair but any issues I'd trade it. Sorry you have to deal with this.

 

[14v6]

Often, it's from manufacturing. Honda has plenty of forum posts with this issue. I remember with a brand new CRV in 2015 I saw a drop and some residue where the trans and engine meet. I cleaned it and fortunately it never came back but the CVT ended up failing at 62k due to a manufacturing error.