A question about split/combined palettes

So, I tried to submit the GB Studio Game Boy Color default palette, but it was rejected for being a split/combined palette. So I have a question; what counts as a split/combined palette? There are a few palettes here that could theoretically be considered as split/combined palettes but aren't.
Can you please clarify the meaning of the term further? Thanks in advance.

It probably is considered "split," because it would be preferred to have GB studio as one entire palette rather than divided into the different options it provides. It's also possible a GB studio palette has already been submitted so they didn't consider it necessary to have a subset of that palette available in addition.