Are your two PVs on the same phase, or on different phases? If both are on the same phase, then yes you can do that, and the CT will measure the sum (or the difference if the currents flow in opposite directions). If the PVs are on different phases, then you will measure the vector sum of the currents, which will not give you the answer you want.
I don’t think they say that. They say, for a normal installation, don’t thread both line and neutral through the CT, but if you look on the “EmonTx - Use in North America” page, you’ll find diagrams that show exactly as you are suggesting.
(And your English is better than my French, so don’t worry.)