SEID is not a research definition. Its a clinical definition. As a result it would have to be modified/operationalized for SEID to be used in research. That will take time. Several years potentially. Then researchers will have to start using it. In the meantime the CCC will continue to be used. For some time after that, probably years, CCC and SEID are likely to be used side by side, just as CCC and Fukuda (with PEM) are now.
Most of the best research these days is CCC. When was the last time we saw anything good from Fukuda cohorts?
In the long term SEID is potentially a dud definition because the advancing science will make it obsolete. However this also applies to every other definition we have.
Now psych studies in the UK still use Oxford. That is likely to continue as they seem cut off from the main research. Or when they use other criteria they use operationalized versions that turn the criteria into something almost unrecognizable, like they did with the London ME criteria in the PACE trial. I think the P2P got this point right - its time for Oxford to be retired as a definition.
PS. So no, I don't have concrete data. Nobody is tracking this stuff. I put this reasoning out for commentary. If anyone has reason or evidence to think its wrong they can reply.