And even if that was true, how hard would it be to create more?
For a nation state like Russia, extremely easy..
Maintaining chemical weapons are much less about storing a fixed number of warheads and more about maintaining the capability to make the chemicals involved. While modern chemical weapons are very stable and can be stored for a long time (as opposed to older ones which would decay extremely quickly), there's not much reason to do so as they supposedly only exist for research purposes and no government would ever admit to stockpiling them for use as weapons of mass destruction.
But in the 80s it was possible to make sarin using commonly available industrial and agricultural chemicals using a fairly basic chemical lab setup, provided you didn't mind an extremely high risk of accidentally poisoning yourself. It would be a lot harder today because a lot of those chemicals were taken off the market or restricted after the Aum Shinrikyo incident (in which they did exactly that). That said, the so-called Islamic State had a chemical weapons program, and while it seems like it didn't go anywhere there is really no obstacles to an entity the size of a state throwing together chemical weapons quite easily.
Adding to this, chemical weapons are one of the few areas in which Russia actually is kind of a world leader. The Soviet Union had a really advanced chemical weapons program. However, the goal of this program was primarily to make poisons that would be hard to detect and could be used for the assassination of individuals.
As battlefield weapons, chemical weapons (well, nerve agents anyway) are a bit questionable. Because even tiny doses can really mess people up, there's a very good chance that anyone using them is going to end up poisoning their own side too. The primary utility of chemical weapons is as terror weapons, because they are absolutely terrifying, extremely cruel and very, very difficult and expensive to protect yourself from but this means there is also a massive, massive taboo against their use, and doing so is going to come at a massive diplomatic cost.
Also most of these weapons, if not used at extreme range and in perfect conditions, would have been suicidal to use... especially naval shit like the nuclear depth charges, torpedos and anti-sub rockets.
That feeling when you realize the Fat Man from the Fallout games wasn't just a funny joke and basically existed.