The way I have seen it explained:
Sanctions are temporary policies that to provoke a change in the behavior of Russia: especially to reduce ability of Russia invasion/war. for example by curbing the country’s revenues from hydrocarbon exports.
Russia’s central bank holdings are already frozen and will remain so as long as the war continues. If Russian reserves are not given to Ukraine during the war, chances are these assets will be used as partial payment of reparations that Russia will eventually pay as part of a peace agreement.
Many policymakers, like former U.S. Treasury Secretary Larry Summers and former World Trade Organization chief Robert Zoellick are in agreement that transferring the assets now makes sense as a deposit against the future reparations.
Eventually the U.S. government ends up just giving the money back in the form of some kind of agreement over Iran’s nuclear program.
And now we need to move past sanctions and impose a NATO and EU wide trade embargo on Russia.
No trade of anything with them. Their citizens living in our countries are sent back to them. Their ships and planes banned from our waters.
No more being nice to them.