I'm not sure -- I recall OoT taking much longer to beat, at least without a guide. A fair bit of it is that it's a harder game, and I recall me taking more time to 100% it, especially because of the Golden Skulltulas. The Poes in TP are a joke in terms of time consumption compared to the Skulltulas. In terms of actually executing the side quests, I suppose TP would have taken longer, but I breezed through most of them, whereas I took more of my time to observe my surroundings in OoT, and worked to solve the side quests via Gossip Stones and dialogue, which took up time in their own right.
ALttP definitely seemed longer to me, because it was a very difficult game, and the sidequests were very few and hard to figure out. Because of their sparsity, it felt like much of the time taken to play the game was spent trying to figure things out, dungeons included. It had roughly 13 dungeons, if you count Hyrule Castle both at the beginning of the game and again after getting all the Medallions.
I believe that ALttP is also longer (and harder imo). Plus less of that is padded out with storyline and cutscenes.
This is a solid point, because ALttP was mostly gameplay, and it was certainly heftier in that department.
If you consider the second quest, the original LoZ is pretty darn long, too -- it had 18 dungeons! Without a guide, it took easily upwards of 80 hours of my time.