This is wrong, see the red highlighted text;
As you can see, the rules are self-explanatory and no need to add a 'specific' rule to explain them further.
I see where you are coming from, however, there is no need for this, see my quote above, you are allowed to create a personal shop in the Shiny sub-forum, and shiny collectors go to the said sub-forum to look for shinies, not the personal shops, so I don't see a point in implementing this.
Although, you could include links to your Item/Shinies Shop in your Personal Shop.
As to why you see there are couple Personal Shops with shinies/items in them, it's because there was only 1 busy TMod for months and couldn't handle all the sub-forums alone.
-Locked-