Granted, they could call them up right away. There are reserve units who are better at somethings than active units...especially transport units. Speaking of transport...
Interestingly, we are rotating our active troops through Europe. A number of brigades of different divisions are being rotated. If we ever do have to fight the Russians, we will have a lot of soldiers from all the major divisions familiar with the Eastern European theater terrain, with maps prepped, etc. Russia has to be aware of this.
Granted, it seems like overkill to me. Unless the Russians are gearing up to attack Poland or something, it seems like we should just maintain the status quo, and make the Germans nervous enough to call up their reserves if they want. I wouldn't be surprised if we are spending more money on these troop rotations than we are on arms for Ukraine.