What does this currency become?

A transferable point is not really a point. It is an option on a few dozen airline and hotel currencies, and every publisher that values Amex, Chase, Citi, Capital One or Bilt points is pricing that option rather than a fixed thing.

Which means a transfer is a trade: you give up the option and receive something specific. On the published figures that trade usually costs you value, and the ratio on the marketing page tells you nothing about whether it does — a 1:2 ratio can be considerably worse than 1:1. These tools price the trade, and show the ratio it would have to hit to leave you level.