I chalking up the no workshirts to factory/production issues. IMO there is a snag preventing them from making workshirts right now.
The demand seems to be there
We have seen reasonable materials roll through in other forms, so there is no shortage of material.
And even at that you don't have to offer 10 variations. Offer 2 or 3 over the course of a 3-4 weeks.
But, if you want a plaid shirt you can have any of the 100 that campaign monthly...
I'd agree if Gustin hadn't said the reason they don't offer many workshirts is because they don't sell fast enough.