I don't know for sure on the really tiny ones, but I would imagine it's about the same idea as with the bigger helis. You want it to be tight enough to hold them in place so they don't get jerked or wobbled out of place when it's spooling up, since can give you nasty vibrations and potentially tip the heli over.

You do want them to be loose enough that a flick will knock them back a big in the grips though. Not all the way back, but make sure it does move. This will take some stress off your drive train in case of a bladestrike.

Centrifugal force will hold the blades where they need to be once it's up in the air as long as you don't have the grips way too tight, so don't worry too much about getting them perfectly straight and lined up and all that before taking off. Just get them close so it won't shake around spooling up.

But yeah like I said I don't have personal experience with the tiny ones, for all I know you might leave them a lot looser since the blades have less mass? Still seems like it has enough relative to the rest of the helicopter that you'd want them to stay in place, seems like it could still potentially shake it up pretty good.