I believe the reason why no one dumped the ROM out of that port is because it was a homebrew game that was being sold by the original creator.A bit of a double-standard to say they won't dump a homebrew game but will dump corporate-produced games.
But I suppose because it's a homebrew they won't dump for one of two reasons: either they feel more sympathetic to a homebrew dev who they see as a person than a corporation who they see as faceless.
Or, of course, scarcity and collecting for resale is probably a factor too.
I've heard collectors weren't too keen on dumping Nintendo World Championships in the early 2000s because they were afraid it would devalue the cart (though on the contrary it has gone up since then.)
I think a gray NWC was worth around $3000 in 2000 (that's about $4,300 after inflation), gold maybe $6000. Now it's, double that at least, maybe triple (beyond simply inflation).
Likewise Stadium Events jumped from $1000 loose (when it was properly dumped in 2003) to about $3000 last I checked.
Having the ROM dumped certainly hasn't reduced their value.