In DSS only 5G UE is aware of it, so whats happens to LTE UEs?

In DSS technique it is mentioned that only 5G users will be aware of it, and not LTE.
So what does it mean actually?
If a UE latches on 4G then it can not go to 5G?

It means for all LTE UEs those frames are either noise or empty.
Same as CSI-RS signal in LTE Rel10 is noise for Rel8 UEs.
Previous version of UEs cannot interpret those frames, and thus are not aware of what’s happening.
But if the UE actually starts NSA, then it sees both 4G and 5G frames.