Yes that screenshot is not evidence that AMEX is the merchant funding facility.
However, Splitit confirmed you can use your AMEX card with Splitit on GEMSNY. Meaning they are obviously working on something. Perhaps this is a pilot for a bigger partnership like we’ve seen with Visa and MasterCard.
In terms of Merchant Funding Facility, my suspicions are AMEX as I’ve stated before it makes the most sense for them to own the end to end process.