That message has already been fixed for 12.20. Thanks for the report though. :)
This thread was added on March 09, 2020, with posts from RebelAndroid.
Original Post
https://i.redd.it/t1oaw1xlqnl41.jpg
Aren't NFL skins not allowed in STW? It said so in the Item shop description
Nope, you can use NFL skins in StW. :)