Mosses like it cool in drystart, rather cooler than the plants.. If you look at nature, terrestrial mosses love to grow at the coolrer shaded spots. (Northside of the trees and rocks) I see it also happen in my north side garden where a lot of mosses grow, i see a lot of moss die in the summer even on very wet spots, just because it gets to much light and probably to much warmth by the sun.
Especialy Fissidens is a rather dificult dry start moss.. It is agonizingly slow and very temp sensitive.. I have some in a bottle on a piece of wood on the window sil.. It grew fine but not much all winter long, now in the summer all turned brown. There is no real benefit in drystarting fissidens, it grows faster and more secure submersed. You likely also will buy the submersed form. So waiting for it to transition to dry invironment, grow and then back to wet again takes a time span beyong drystart periode. It likely survive the 6 to 8 weeks a normal drystart is practiced but it will not bring you any wonders.
Only if you put the moss in a blender and brush on the pulp, you need to wait till you see it grow and attach before you flood. That i never tried with fissidens or any other moss.. If you flood before its growing and attaching you flush it all off with flooding.. But in a way, buying fissidens you will need a lot and spend quite some cash to have enough to put in the blender and get something out.