Close. The INF Treaty does not limit ballistic missiles to 300km but 500km which is why the Iskander has that range.Due to the INF treatry Russia doesn't have ground lanched longer than 300km range munitions, designs and manufacturing capacity.
USA scraped it in 2019 august, means there wasn't enought time to re-calibrate the Russian industry and create new designs.
Iran hasn't got restrictions like this, and developed huge insdustrial capacity for this kind of munitions.
Cruise missiles do not have range limitations however. I think the whole treaty was a raw deal for the Soviet Union who had to give up their IRBMs without the US giving up their naval cruise missiles but that is what they did.