There is a bit to unpack here.

1. Transactions are replayable between RDTS and Bitcoin. Any transactions sent on either are also eligible to the other chaintip unless they spent UTXOs that only exist on one chaintip.
2. Nodes that run RDTS will reject blocks that don’t signal for RDTS activation. Currently, there have been zero blocks signaling readiness in this and the past difficulty period. They got 3 blocks in a difficulty period once at the peak which corresponds to about 0.15% hashrate adoption. Should the current hashrate adoption be maintained, RDTS nodes will simply get stuck below the height of the first block that doesn’t signal during the mandatory signaling period. They would still see the unconfirmed transactions paying them, just have no information of what actually got confirmed.