Maybe I'm just dense and there's some weird psychology thing FB is doing here. but I can't think of any reason why ignoring search parameters would be intentional, especially for a classifieds search! Even if it's for sponsored listings, they're just bogging down the conversion rate.
If FB marketplace is showing me a thing I can't buy because it's too far away to pick up, doesn't fit in the space I'm specifying, and over my stated price range, I'm just going to assume there were no results and look elsewhere. I guess FB gets paid for an impression, but an advertiser that sees impressions going up and conversions not changing is a pretty unhappy advertiser.
Yeah, I'm sure the newsfeed is an example where ignoring settings/search params like this works, because there's no real hard-lines to what posts someone will be somehow able to read other than maybe the language it's in, and even that's flexible. You can just blast users with whatever slop pays FB the most. But some sponsored decor tchotchke being 500 miles away might as well be on the moon.
They don’t actually give a shit whether you find what you were looking for, they heavily optimize for their time-on-site metric. If the search results were terrible, and you had to refine your terms and try again, that’s more time on site! More time is more better!