I don't know about the 4-5 hours playtime, but I've played the mission on Normal and yeah, it took me ~2 hours (though technically I could finish it sooner, I just tried to explore optional areas), so with the additional objectives I can imagine that estimation is correct. The mission perhaps relies on the player collecting the scattered loot a bit too much.
I'm not sure what kind of correlation could be between the release of TDP and the increasing amounf of ratings Into The Odd has, but I've seen it being mentioned quite often whenever a new player dropped into the community and asked about cool fan missions they can play. Also, Into The Odd has an easily to remember title and screenshots featuring daylight sections - which the majority of fan missions don't have.
Just my guesses.
Either way, it's a cool milestone!
Thanks for the tip, but I've been aware of that (so much so, I even rated the missions before posting the review).
While I didn't expect the categories to get rearranged in this way, I thought it would be cool if readers could easily see what I thought about the individual missions rating wise.
Not sure if you plan to polish the custom categories in the future, but I think the feature has a fun potential. It's a little bit shame editing them is a bit chaotic and unreliable.