As I understand the issue ...
Each power strip allows plugs to be inserted into its recepticles. The only restruction is that the plug be 15amp.
Each power strip allows its plug to be inserted into any 15amp receptical. The recepts on power strips are rated at 15amps.
There is no code violation in daisy chaing power strips.
The words in the listing "not intended" does not mean "not permitted."
