I think you should be looking in the mirror when you ask that question.
I suspect Putin DID, and he may have had a say in writing them.
I believe they all specify the payment terms and typically it will say USD or EUR.
Don't care what you "believe", what do you know for a fact?
So he is trying to change the terms.
Maybe yes, maybe no, what is certain is it will get into court to be determined.
Which he is welcome to do upon contract expiration.
And may have done when the LAST contract expired.
Actually PUTIN admits he can’t do it. So he does this instead:
https://www.msn.com/en-us/news/world/kremlin-demands-rubles-for-gas-leaves-currency-loophole/ar-AAVI50R?ocid=msedgdhp&pc=U531&cvid=5ae2d602af7b49208df7c52fe9bc559b