Shorts creators can link back to the full video, assuming both are posted on the same channel. You can't link to someone else's video though.

Also, a channel that posts shorts exclusively needs like 30 million views to be monetized, you're infinitely more likely to reach that threshold creating compilation of cute cat videos than with your own original content (regardless of the niche). I'd be shocked if even 2% of channels earning money from shorts create any original content what so ever.