There’s no structure present for light absorption. Pull the thing and start again.
plumule can still fully develop true leaves as an Acotyledon. From a scientific standpoint. the plumule is the light absorption material and proof is in its standing straight up. Just to share some knowledge. But you are correct in that it is significantly reduced and can reach the point it decides it cant develop true leaves and aborts. Which you would know if it drops to the ground and stops standing at attention
A common misconception with Acotyledon development.
edit: I've never had a cannabis acotyledon before so can give no advice. i do know some require a split on other plants with a razor blade to push out first set of true leaves. I wouldn't do it with my first one because I would like to know if a cannabis variant can push them out for science. So I hope he lets it grow cause from a science standpoint this is fascinating to me.
Edit 2:
If im being 100% honest after staring at this for almost an hour
THis plant reminds me of a seed that germinated and still had the shell on the cotyledons and I went to remove the shell from the cotyledons and ripped them off and all that ended up left was a standing plumule connected to a root. I say that cause typically the plumule is shaped like the seed but it does look like it could have swelled up some trying to force a split. But at face value it looks like a sprout the seed got popped off. But I hope for science it is an Acotyledon cause i'd love to know.
edit 3: i almost feel like it will need a slit to expose the shoot primordia its a real gamble idk what my vote would be. Other than to leave it