Yes, I stand corrected on the Soviet-era air-to-air missiles which have been reliably decommissioned and destroyed. However Russia may have held onto many SA-300 compatible nuclear warheads as this linked presentation alludes to:
https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%20Room/Science_and_Technology/06-F-0446_DOC_10_The_Nuclear_Weapons_Policy_of_the_Russian_Federation.pdf
See p. 23 of the PDF.
The current generations in use of the S-300 are not nuclear capable. And your own reference says nothing of the kind.
It talks about their missile forces, but that is not their ADA forces. Soviet-Russian missile forces are those that have offensive weapons to be used against ground targets. Like ground attack cruise missiles, MLRS, and things like that. The air defense systems fall under the Air Defense Forces, and not the Rocket or Missile Forces.
And sorry, but I pretty much have to reject that reference anyways. It provides no sources, no references, and is really just a bunch of random quotes from somewhere with no real factual or contextual information at all.
But it is not even that they destroyed their air to air nuclear missiles, I have never found any source that said they had ever developed any in the first place. The two I listed were both US systems, but I would be interested in knowing what Soviet ones you think there were as I could not find any listed at all.
And the INF treaty was signed way back in 1988, and went into effect in 1992. I can't see either the Soviets or Russia holding onto 30 year old nukes. Especially as they would have been for a system (S-300PS/PM), which was only in use for about a decade and was retired long ago. And the missiles would not be operational, so they would have had to construct entirely new missiles to use them. Air Defense missiles only have a "shelf life" of around 10 years. That is why each year a lot of units at Fort Bliss get to go out to White Sands and play with them. They have already reached their shelf life, so it is often better to use them in training instead of simply destroying them.
One must pay attention when talking about equipment like this, as just saying "S-300" is not really enough. They have gone through many variations since the system was first fielded in 1967, and the ones that even could have fired nuclear tipped missiles are long out of service. Along with any that would know how to operate them in the first place.
The current generation are not even known as the S-300 (SA-10 "Grumble") anymore. It is actually the S-400 (SA-21 "Growler"), as the system has had so many changes and upgrades that it is barely the same system. The system they developed for using the nuclear variants of the missiles were the S-200PM and S-300 PS. Those were retired after the INF, and replaced with the non-nuclear S-300 PMU series, and now the S-300V series.