I think you're correct a long-term push is different from a 72 hour scramble but they're only looking to "win" an interview, not a place in a starting class. I think it's reasonable a team could be unsuccessful at filling out an application (which previously required an idea) but still be extremely strong candidates. I hope YC accepts, they don't stand to lose anything (save time) and there's no obligation to accept similar copycat offers in the future. They might also get a problem solved.