Just saw this on my Amex Platinum. Looks like it's a flat $75 x 2 credit, no minimum spend.
Save offer to your Card by 25/06/2021 & spend online or in-app at NET-A-PORTER or MR PORTER to receive your purchase amount back, up to $75 per Card. Offer available twice within a calendar year. First credit is valid on spend made by 30/06/2021. Second credit is valid on spend between 01/07/2021 - 31/12/2021
Everything on the website is ridiculously overpriced, but there's a few options for $75 freebies. Can't complain, I guess.
Damn, not on my Explorer.