Casting an editorial eye over the rules, the Sub-Attributes aren't clearly labelled in the text with the Attributes that they belong to.
You probably know it inside out as the designer and it may seem obvious to you.
However, this might be someone's first TTRPG or they might be a casual player not used to working out those sort of details for themselves.
That said, I see that the Character Sheet has that info.
Also a well laid out Mechanics Quick Reference or GM Screen would be really handy. That would also be an excellent place to make sure that the Sub-Attributes are properly tagged with their corresponding Attributes.