Voiding warranty

[Saltzy]

So, I work in the NYC area and decided to stop by the service center in the Rolex building on 53rd just to have them take a look at a used Sub I bought to ensure it was legit, even though I was 99.9% it checked out, which is what I was told I should do by an AD as the best way to do so.

I had the warranty card with me and handed it to the customer service rep when I handed it over, which had the name of the original purchaser crossed out with a sharpie.

15 minutes later they came back and told me the watch checks out, but that any remaining warranty time (which is over 2 years) has now been voided because it had been bought from someone that was not the original owner.

As long as nothing goes wrong the next couple of years it's not a big deal, but I'm just curious if this is standard/am I a moron for showing them the warranty card with original owners name crossed out?

Thanks.