How is this different from using an ORM that supports both dialects using middleware? I mean I know it's clearly different, I'm just saying I'd rather use an ORM that supports both dialects. Seems like less overhead and same basic functionality.
I don't think this should turn in to an ORM or not debate, but there are plenty of reasons, especially for the crowd that would do anything to avoid ORMs. Just try to take a peek into the multitude of "ORMs are bad" articles / discussions.
For instance - I would love to be able to use https://github.com/porsager/postgres with sqlite.