IAF used Su-30K (not MKI) as a mini AWACS using datalink to vector MiG-21 to attack from directions outside the radar coverage cone of F-15 & F-16 and that surprised the Americans because they thought IAF operated under strict GCI like a straitjacketed communist.
So yes, the Su-30MKI was "covering" the MiG-21 Bison. But not under its wings or fuselage It was "covering" by letting MiG-21 approach from a different direction without using its radar.
The other feedback was MiG-21 Bison with HMDS and R-73E could make snap turns and how it was small and hard to spot, but that was the case with Gnat too.
With 240/360 degree AWACS coverage instead of a fighter radar cone of 70 degrees, the above tactic would be useless.
They made good decisions about when to bring their strikers in. The MiG-21s would be embedded with a (MiG-27) Flogger for integral protection. There was a data link between the Flankers that was used to pass information. They built a very good (radar) picture of what we were doing and were able to make good decisions about when to roll (their aircraft) in and out.”