Here a clearer image ... but I still have no idea!
View attachment 87651
But if you read the comments they are also suggesting him to be a Russian (IMO clearly not)
Just for thoughts. In one of
Shilao's podcast, they mentioned that the
military attaché of foreign (mostly US) embassy in China always fly Chinese planes for accruing flight hours accompanied by a Chinese pilot. This may be one of the possibilities.
They also mentioned that the Chinese side, with good intention, provides advanced trainers to the dismay of the attachés because they intend to fly something more exotic and old-school, like J-7s.