Yes, parse out HTML comments which is also kind of trivial if you've ever done any sort of parsing, listen for "<!--", whenever you come across it, ignore everything until the next "-->". But then again, these people are using AI to build scrapers, so I wouldn't put too much pressure on them to produce high-quality software.
It's not quite as trivial as that; one could start the page with a <script> tag that contains "<!--" without matching "-->", and that would hide all the content from your scraper but not from real browsers.
But I think it's moot, parsing HTML is not very expensive if you don't have to actually render it.
Lots of other ways to include URLs in an HTML document that wouldn't be visible to a real user, though.