The other restrictions prevent the same issue. OP_RETURN is not the only contiguous region that can be abused. There is no "different issue" addressed by RDTS. There's also no evidence an OP_RETURN-only variant would get more support, and someone even proposed that a while back and effectively proved it doesn't. This has only just become an attack vector 4 months ago with the release of Core30. And reversing that harm is the only thing RDTS accomplishes.