Pay-with-Points assigns an arbitrary fixed value of $0.01/point. A 50% rebate is only a 50% discount if you accept that $0.01/point is a fair value, but points are worth more than that if transferred to a frequent flyer program. All of the card issuers play this game because it's easy to think that a point = penny, but points are worth what they can buy, not what the issuer assigns.
Peeling back the onion here.... AMEX has generally had a 1:1 exchange rate over the years, but now it's much easier to accrue MR points w/ the various category multipliers. And of course, there's also dynamic pricing to contend with. The one thing about $0.01/point is that it's fixed when booking/redeeming through AMEX travel portal. Nothing new here, but I do come to a different valuation conclusion because of dynamic pricing.