I don't think the T&Cs from March make much difference.
I submitted them to Amex, but then TravelUp send Amex their new T&Cs and then Amex just kept deciding in their favour!
I even uploaded a separate cover note asking them to check the T&Cs that I uploaded vs what TravelUp are sending them, but they just go with whatever the merchant's latest response is.
Eventually I managed to get this closed off as I was able to use TU's automated refund form via their website. The refund came through on my Amex card but minus the £50. Hence I am now disputing the £50 but at least I 100% got the rest back now.