google what is the difference between an adverb clause and a reduced adverb clause? ... many hits First hit: (actually a good acticle) https://www.thoughtco.com/reduced-adverb-clauses-1211106

Can I say that as an educated American I have no idea and I would have to look it up. That tells me that the difference is unlikely to matter to your language learning efforts. It’s probably better for you to study vocabulary and usage than it is to study such fine grammar details.