I have seen a couple posts about this but they don’t go into much detail or provide many sources. The short of it is, in real life some variants of the Su-30, especially those with al31FP (Su30SM, Su30MKI) should have the ability to engage TVC, or re centre / disengage TVC. This is useful in situations where TVC actually hinders you such as in rate fights, when you are in BVR and trying to maintain energy, when you are slow speed and trying to aim shots with things like AOA button off yet your thrust vectoring keeps flinging the nose all around and making more difficult than usual to aim. Adding such a feature would also future proof issues with Al41 variants of Su30 coming to the game, and Su35.
The only issue with proving this is that the Su30 is a modern aircraft and the availability of manuals or high quality images of the cockpit are hard to come by. However there are multiple sources stating without photo proof however that ‘‘The main difference between the AL-31FP engine and the serial AL-31F is its nozzle, which can swivel within ±15°. The nozzle’s axis of rotation is offset by 32° from the longitudinal plane of symmetry, allowing for differential deflection of the two engines’ nozzles to generate not only vertical but also lateral thrust components. The thrust vector control system on the Su-30MKI is integrated into the aircraft’s fly-by-wire control system and has no separate control levers, but can be completely disengaged if necessary, locking the nozzles in a neutral position.’’
https://military.wikireading.ru/hqT8Na4jKl from a Russian magazine around the time of MKI deliveries to India
Understandably this is not stating the Su30SM, however gaijin has added Al31FP to both aircraft (Su30SM, and coming SU30MKM MKM being the malaysian variant and being a copy of the MKI indian variant). And considering gaijin has given Su30MKM the ability to carry things it never had i believe anything to do with any variant of the Su30SM should and can be replicated without finding direct sources for all 3.
Although there are not yet any sources stating Su30SM2 can have this ability as the base Su30SM is still in transition to the modernised variants, i would personally believe to also be an option as previous Su30SM variant with Al31FP, and Su35 with Al41 have it, possibly making it cross compatible.
To future proof this feature to Al41 on Su30SM2 and Su35, russian sources claim that ‘‘Design-wise, this engine is a further development of the serial AL-31F, utilizing fifth-generation technologies. Equipped with a rotating nozzle, combined with the ability to automatically vary the thrust differentially between the two engines, known as differential thrust control, this engine ensures aircraft control in all planes, including at extremely low and near-zero flight speeds. Conventional aerodynamic controls become ineffective under such conditions. If necessary, the thrust vector control system can be completely disengaged, locking the nozzles in a neutral position.’’ from RIA.RU https://ria.ru/20080707/113394586.html?utm_source
All we can do is speculate and hope this feature gets added , as it won’t really be a buff or a nerf for these vehicles, and more of a quality of like difference just like with the addition of the AOA limiter button. Having seen that multiple russian military news outlets state this i hope it would be pushed further. However i understand if not as again they are not direct evidence based sources (i would say myself that enough sources say that it exist for it to be fake)