I have actually seen this single leaflet thing happen before even when it wasn't a "reveg":
Last year I had a Chem D seedling and let my soon to be Father in Law take a clone from it, and once it was rooted and growing, it legit had a bunch of those single leaf things all over the place, even though the plant the clone came off, didn't have that at all.
Now, the only difference between the Mother I grew out and flowered outside, and that clone, was that clone being done inside a tent with LED lights.
Maybe the lighting has something to do with it ? I had clones of Blue Cheese in that same tent and once they were rooted I put them outside and let them run, and nothing like that happened to them. It was odd bro, like, I'd peak in the tent and see that Chem D clone sitting there with like a whole section of branches having single leaflets on it, all the while the outside seedling did great.