I think he means the modular reactors.
AFAIK RR's units haven't finished full certification which could take several years.
EDF on the other hand have a bunch of reactors of a certified design and a very experienced and streamlined construction & upgrade team, so the they'd basically be able to start building as soon as planning permission and financing is sorted.
RR's design is from what I understand faster to build but could be delayed for ages, so the sensible thing is to fast track the design that is ready then once the RR units are confirmed use them to for additional plants (basically use the EDF ones for example to replace some of the coal/gas/oil plants and the nuclear ones, then the RR ones to replace more of the coal/oil/gas ones).
It's insane that we've known the expected shut down dates for all the power stations for decades, yet because of none of our wonderful politicians wanting to do something that will be unpopular in the short term (or for that matter understanding the concept of inflation or forward planning) they've dithered over it until we've hit the point where it's basically too late to avoid problems even without things like Russia invading Ukraine affecting oil/gas pricing.