Seems like these exchanges just need an excuse to confiscate funds and keep it to themselves.
Unless they are going to send all the confiscated cryptos to Ukraine's donation address then I am against it(whether it's targeted or not). It won't be less than a scam if they choose not to donate it.
If they are going to donate 100% of the confiscated cryptos then target only oligarchs, politicians and their relatives/friends.
Unfortunately there are laws regarding what happens with that kind of money. Many assets of the Russian oligarchs have been seized and they are all sent to certain government places to be kept there, like a hostage. This means if Russia stops war and gives the lands back, then European countries will pay the oligarchs their assets and money back, or at least money because some of the assets are gone already.
Same goes with this, you could seize the cryptos of Russians and then name by name give it to government how much and owned by whom. In that regard if the war is over, it could be sent back or credited back. That's the important key factor to make sure Russia has incentive to stop.