I recently had an opportunity to test my CT+energy IC based monitor at various crest factors and was impressed at how well it did. At least with the CTs I use, and the 8kHz sampling rate the energy IC uses, it got impressively close to a reference meter that had no magnetics.
I set an AC lab supply to 230V, 50Hz and a programmable AC load up in constant current mode, and tried out various crest factors… the highest being 3.5.
The output of the CT looked like:
and here’s how it looked from inside the energy IC, after all the LPFs etc.:
Then I compared the monitor results (“ERM” column) with a reference meter (“Meter” column) for real power, power factor, apparent power, distortion power, and reactive power at various crest factor settings:
I’ve since added another digit to my PF display and get a good match there too. The shape of this load is different to your dimmer, but it does at least demonstrate that some pretty nasty looking signals can be passed through a CT.