I believe we used these exact pulleys on our 2012 bot drivetrain. They are plenty strong. We used the KoP plastic pulleys last year, as they were cheaper and lighter. They also worked just fine.
On a slightly related note, my car has plastic timing belt pulleys.
BTW, the link you posted got altered with the parenthesis and quotation mark in the sentence. Here is the link for anyone else:
https://sdp-si.com/eStore/Catalog/Group/218.