is लेओ an acceptable variant of लो or does it not exist? i found it in wiktionary, perhaps the tables there are just automated somehow based on preset grammar algorithms, so that's why it's rootword+ओ, idk. other sources clearly state that this verb, along with "to give" and a few others, is an exception in the imperative
The vowels in Hindi can never stand alone behind a consonant. They always have to be merged into one. Aao (sorry, no Hindi keyboard) has only vowels, so they aren't merged together. But le-o gets merged into lo. In common speech, some people do say leo, but it's not the normal way of saying it. I haven't seen how far this course goes, but if you get to sandhi (putting two words together to create a new word) then you will get a better explanation.