UOB has updated their website.
http://www.uob.com.sg/personal/cards/credit/one/
Scroll all the way to the bottom till you see Terms and Conditions then pull down to see.
Wef 16 Mar 2020, please be informed that selected transactions such as Grab mobile wallet top-ups, wire transfers, payments to Non-Financial Institutions (such as crypto-currencies etc), quasi-cash and more
will be excluded from the awarding of cash rebate on the UOB One Card and bonus interest on the UOB One Account. For clarity, all other Grab transactions will continue to be eligible for the awarding of cash rebate on the UOB One Card. Insurance payments will be excluded from the awarding of cash rebate on the UOB One Card but continue to earn bonus interest on the UOB One Account.