True. On the part of invading Ukraine, it would be a long shot with no obvious benefits.
There are indications that this possibility has been discussed in detail in past years. The fact that Russia can make such statements means Cuba's assent is not a presumption. Remember, Russia has been Cuba's guarantor against US invasion since the Cuban missile crisis. Even though Russia abandoned communism, it has continued to prop Cuba financially, obviously because of the Island's strategic position. For Cuba, hosting Russia would mean more income, security, and a good incentive for the US to abandon sanctions against the Island.
In these proxy wars, the US never gets a free pass where Russia is involved. For instance, the Russian defense systems deployed in Iran dissuaded the US from executing spiteful incursions even when manic Trump was in charge.
Russia is worried that China will stink for everyone the moment it gets ahead. When Russia sold China its most advanced fighters last year, China had to promise not to duplicate them. Of course, no one would be totally comfortable despite the assurances because China is China.