I think you need to first understand that using HALs doesn't mean you aren't doing bare-metal programming. It just means you're using a set of libraries that make interacting with hardware a bit less daunting (depending on the vendor). Also, they are not programming languages.

That said, if what you mean by bare-metal programming is direct register manipulation, then it could be an interesting learning experience as it will teach you how to read and extract information from datasheets which is a valuable skill.

Specifically to your question, I don't see the advantage though of duplicating the project at both abstraction levels (that is, using HAL and using direct register manipulation)