We often (didn't you OTB??) use the phrase e.g. "climb to non-standard F410" to highlight to the pilot that they will be operating contrary to the standard FLOS
I did frequently, pre-RVSM, but I'm not sure how many understood the implications let alone appreciated the effort involved. I wouldn't like to think it was being done on the Mainland though and I'm sure it's not. The word "cannot" springs to mind.
"On standard" sounds the more likely, if obviously confusing to some pilots, terminology.
Of course this would all be academic if China fell into step with the rest of the World and adopted FL/feet as the universal "standard". Funny how they can adapt to Imperial Flight Levels through South Sanya airspace. They might appreciate the problems more if they had to do the transitioning to/from metric levels in their airspace rather than relying on Hong Kong to do it for them in HK airspace. But, hey, that's why you get paid 200X more than Mainland controllers.
On the beach (watching contrails)