They are the same species, but it's a Brussel-sprouts vs Broccoli type situation where they started as the same plant but have been selectively bred for different purposes

The THCa/Delta8 stuff is not brussel-sprouts vs. broccoli. They difference is in timing around harvest and process. They're growing many of the exact same cultivars as what is sold in a proper dispensary (and indeed, much of what is sold in dispensaries would actually qualify because they actually have very low levels of Delta9 in them)

You can effectively just under-cure the exact same plant and get something that comes in under the limit.