He is probably referring to the carbon generated by the construction of the facility, which is still orders of magnitudes less than a coal plant over its lifetime.
I mean if we're talking lifetime emissions even the IPCC places nuclear pretty fucking low and refers to it as a low-carbon energy source. So I don't think anyone should be to blame for using that term. It's the exact term used in the scientific literature...
A lot of this is also kind of silly accounting. For example, if you have to put materials on a truck to build the plant, and operate construction equipment, and these things burn diesel, you can count that as CO2 emissions. But you can also use electric trucks charged from non-fossil fuel generation and that goes away.