Isn't this the F22 style nozzle?Lyulka developed a new stealth nozzle for Izd. 30 engine.
It is for a penetrating bomber.From what I get the main reason why the F-35 uses the round nozzle is because it is cheaper. But it has less IR stealth than F-22 square nozzle.
I do not quite get why the Russians want to use a square nozzle on an engine with 3D TVC. F-22 has just 2D TVC.
Maybe they have a lot of exhausted ones, they are used a lot on the front. You cannot do field maintenance eternally, rotation is necessary so a large number is important..Russia prepping over 4000 units of artillery from its reserve. See all the Tyulpans and Malkas, Zil-131 and BTR-70.