Yeah, I've seen other guys do it. Just watched a video yesterday of a guy using oil based primer with a synthetic (that brush is toast).Chinex is actually really good for oil paints and varnish
Wouldn't surprise me if Chinex is resistant to chemicals, it is a surprisingly durable filament.
That said (on a personal note) I don't use synthetics with solvents. I find the solvents slightly deform the synthetic filaments and shorten the lifespan and usefulness significantly.
I am a firm believer in:
Synthetic for water based
Natural Bristles for oils
I only ever use China Bristle (or other natural bristles) with oils and varnishes.
Part of the reason for this is clean-up.
I never wash 'oil brushes' in water, and never wash 'water brushes' in oil. Mixing them usually messes up the brush.
I throw latex brushes into a 5 gallon bucket of soapy water to soak until I can get to them. Similarly, I will often suspend varnish brushes in mineral spirits and let them soak overnight... a synthetic could not take that without deforming.