Challenge lost in 2 minutes
Nah. You might be able to rush through to the end of Fallout in 14 hours, but a reasonable first play of the game while taking the time to converse with most of the characters, explore, and poke around will be closer to 25-30 hours, and probably more, as the HLTB poll numbers indicate. "Main story" means exactly that. Fallout is pretty tight, narratively speaking, but there's still more to do than complete the main story—and unlike a great many RPGs, it's extremely replayable. In fact, it's so replayable that a person is likely to play it again right away or soon after the first playthrough. That's something I did only with Fallout and Fallout 2 (and then again, and then yet again), but never with any other RPGs until Underrail and AoD were released for public consumption well over a decade later.
But yeah, if you define "completion" as finishing the main story with absolutely no stops along the way, ignore several critical factors, and fudge the numbers, then sure, you won the challenge. That's not actually how I define "short" RPGs, though. I'm thinking of the ones that can be completed in 10-15 or so hours, the whole meat of them, and then you're done with them because there's no genuine replayability/desire to replay.
Fallout is an exceptional and cherished RPG anyway, so rushing straight for it rather than coming up with other examples is about as faggy as you can get. I'm still waiting for more actual examples.