Yeah, the scrubbing does seem a bit flawed. I hate to bloat downloads with garbage data but there doesn't seem to be a perfect scrubbing tool. Ideally I'd like to switch to full copies verified by no-intro, then someday if someone makes a proper scrubber I could offer both versions. The majority of scrubbed games seem to work though, so do let me know when you find problems and I'll hunt down a no-intro verified copy.
I'll check out Need for Speed Underground. It should be around here somewhere.
I notice that your GameCube ISOs are scrubbed. This may save space on file sizes, but there are a few problems that I've noticed.
-Simpsons Hit and Run has the FMVs deleted in the scrub process, not a deal breaker but still pretty obvious.
-Pac-Man Vs., running on original hardware through USB loader, will crash when the GBA is connected. I think the same will happen on Dolphin if GBA link emulation is turned on.
-I've experienced other crashes with your ISOs on original hardware, not sure about Dolphin because my computer can barely run it lol. I remember Eternal Darkness crashing on Chapter 1 when I was trying to solve a puzzle, or maybe that was the sanity meter's business? Wasn't sure if it was your ISO, but I think it was.
As for the missing game, Need for Speed Underground (GCN) has an entry in the list, but there's no ISO.