While Russian tanks are modernized, their firepower and protection is largely the same as they were in 1990-2000. ERA doesn't help if its never installed and modern ATGM and tank rounds can defeat it. The tanks Ukraine is going to get are upgrades of the generation of western tanks that destroyed Iraq's Russian bought tanks - twice?
By June there will likely be a Ukrainian offensive. When that happens, Russia will not be able to blame its tank's performance on export models and lack of skill of a non-Russian army. Which they can't now, since Ukraine is using mostly Russian weapons.
I am reading that we are soliciting Russian type tanks from Central American countries such as Venezuela and Cuba to send to Ukraine quickly in exchange for updated US versions for their trouble.