Add2Basket button in wrong state?

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I have Iron and Wool Readytheme, a Product (no variants/attributes assigned) that is tracking inventory at 0 qty and not hiding the product. When inventory is 0 I expect on page load the Add2Basket button will be disabled. However, it is not.

Seems to be working as expected on variants in products. I am not finding where the problem is and have run out of places to look. Any idea?

Thanks,

Scott