No, it is not merged on testnet, because testnet runs Bitcoin Core.
It was only merged on Inquisition, which is a Core fork ran by AJ Towns that powers the "official" signet. APO was/is also merged and operative there, as well as OP_CAT, see https://delvingbitcoin.org/t/ctv-apo-cat-activity-on-signet/1257/2