And you think this is right? Why spend a day upgrading harpies and tempo on returning Troglodytes back? Maybe I’m missing something?

I think it’s right. Lots of pros. Boosted scout heroes and the main. On the first day, you don’t have to solve super-tasks; the main can hang around the castle, visit some stat booster structures or pillars, no big deal. But on the second day, boosted scouts will scout more and make it easier to build the right strategy — better to stay in place for a day than to go the wrong way. Also, you often run into shooter stacks that are much easier to break through with upgraded harpies. That’s my noob opinion :)
P.S. There’s no major loss of tempo from returning Troglodytes for the upgrade; most of the time on the first day you can get by without fights and just leave them in the castle until 112.