I think that, geopolitically, each side is trying to outflank the other based on current realities.

The US wants war while they still have the petrodollar to fund an offensive military to continue to grab resources.

Russia wants to put a left-hook into the US economy/petrodollar system while parrying via their military capabilities (their ability to defend themselves).

These are current realities. As you say, future realities could be different, and probably involve a race between Russian anti-hypersonic defenses and US development of hypersonics. Both sides will be looking at that timeframe, 3 - 8 years in the future. That is the nature of an arms race. But Russia is leveraging current realities right now to try to persuade the US to back off right now.

Best regards, Shyaku