Say you're trying to rush Horseback Riding (perhaps you're Mongolia or Scythia, or for whatever reason). You're fishing for it, you may even build a pasture and reveal it's behind something. You have a builder with two charges... you put a farm on some rice to reveal irrigation, but it turns out irrigation is not the tech that's blocking you. The tech blocking you is actually Wheel, and you use your final charge on some copper.
And it's not like everything is blind, you can still see the techs you can immediately discover. It looks like the first 3 techs (mining, Pottery, and AH) all turn into the only 3 techs you can research out the door, and then everything else gets shuffled within the eras after them.
It will definitely slow down the early game, since by the time you get that builder and pasture online, it's only then that you start to see if you end up chasing a wild path if you were gunning hard for a horseman rush, for example. The big steps early is trying to figure out where astrology (if chasing a religion) and writing (if you want a campus) fit. But otherwise, I do think it will lead to a little bit more playing the map, since you're going to be more limited in tech choices at any step along the way so with a lack of info will virtually always want to research either the cheapest tech or the one that gives you an immediate benefit, and it might lead you to chase more eurekas earlier just to get a hint of the tree.
Or you just play as Macedon and laugh at this feeble new game mode.