I don't know why all the restraint then. It just adds fuel to the fires of propaganda. Look at our friend here named after some sort of Italian STD. They are able to push this sort of propaganda because of not utilizing full power plus the loss of live for both nations.
I believe it could be an assignment to hold reserves in the event of an unexpected major clash in Europe.
It may be a case of keeping military spending at lower levels than the initial period of the invasion, thus keeping it within the acceptable cost of budgetary spending, not least because there are other priorities of the Russian state.
It may be a case of keeping regular force casualties strictly low, most Russian and allied losses are from fully mobilized LDNR forces, Chechens and Cossacks (these are historical being used as irregular forces since the Russian Empire ).
It may be a case of keeping things that way now because the Russians want some sensitive NATO equipment to reach the front lines in Ukraine and be captured or bought on the black market, as corruption in Ukraine across the governmental and military sphere is endemic. . This claim I read today from a Romanian analyst and it makes perfect sense.
It might be a case of keeping things as they are because it might benefit Russia in some way. One of them is the long-awaited and long-awaited winter coming, where Russian geoenergetic power will give greater weight to Russia's claims while decreasing the political and diplomatic weight of the EU/NATO.
There are so many other reasons here.
Regarding the mobilization and increase of Russian troops in Ukraine, I agree with the previous comments, logistically speaking, Russia does not have this type of organization and competence to carry out this type of large-scale operation at a predetermined time.
The war was already "doomed" on their force structure plans however many years ago these were made.
For example after 2012-2014, the Russian leaders should had taken into account that there was a very real possibility that a big land war would happen witn Ukraine and act appropriately to reorient their military focus, increase/decrease army troops, increase/decrease focus on various fronts, adjust army/navy/air budgets, adjust army/navy/air R&D and procurement
So yeah, although the way the war started was (and is) stupid, the even bigger problem was Russia's strategic failures to plan for this possible scenario in the previous years
But there was an expansion after 2014. Russia had a force of 200,000 and since at least 2021 it has configured a force of 300,000 troops active in the ground force, we can clearly see this when the number of BTGs was expanded from something approximate in a dozen units to more than 160 BTG units in 2021. One of the failures in the modernization of the ground force was the organization which is a separate matter, among other reasons.