It was not just a technical thing... it was unilateral change of a legal contract and blackmail by Russian regime that yet again demonstrated clearly that contracts and treaties mean nothing to it.
Let me complete that sentence for you.... after Finland refused to pay in rubels because the signed gas import-export contract specified other currencies.
Thinking that this is just between Russia and Ukraine is such a common mistake. Ukraine is the latest move in a larger chess game (remember Transnistria, Georgia, Bellarus?) where the end goal of Russian is a new world order. Instead of the current order based on western values and laws, Russia wants the so called "uni-polar world" to change such that it has it's own sphere of influence. That sphere would consist of weak countries subjected either politically, economically or militarily. It sees those as buffer states... and there are never enough of those.
Funny thing that word "war"... By that definition US has never been at war with Russia/USSR yet a large part of last century was called "The Cold War". Kinetic war is not the only form of warfare.