This is an old growers trick for plants that don’t wanna root in the soil that great and look like they are drying out and dying off, I’ve save ALOT of seedlings putting a dome over em for a few days to stay alive till they successfully root, one of the jacks from my seed run was under a dome for 3 weeks till I got it to take, didn’t matter cuz it got so far behind the others and never showed gender after 2 months I ended up just culling it.
Generally once u see the cotelydons ur best just letting it get light but watch it checking on it every few hours that first day or two if it’s continuing to open and grow then let it get light, if it looks like it’s drying and shriveling then throw a splash of water in the top of a water bottle and dome the seedling for another day or two but still under light