Right, sorry. But still this expandable plant plan is still 10% of the size.

No. There are no 3-4 GW(e) nuclear plants. The largest nuclear power reactor in the world has a net electrical output of 1.66 GW(e).

(Clarification: I meant no 3-4GW(e) reactors, not clusters of reactors of that total aggregate output.)

Hinkley Point C consists of two 1600MW reactors. So the claim is off by slightly less than an order of magnitude, not by more than one.

His statement was off by a factor of ~20 (on the power of the reactor; the proper comparison is reactor vs. reactor, not reactor vs. multiple reactors), or more than an order of magnitude,