This move sets a precedent threatening confidence in the western banking system. Is it worth doing just to save finding $300 Billion USD? I don't think that is a good idea. Better for 'the West' to fund Ukraine out of its own pockets than to undermine confidence in its banking system IMO.
While in theory I agree with you, I think that the Western banking system‘s reputation is so low now, that it doesn’t even matter anymore.
Ever since the US enacted FATCA and the OECD implemented the CRS, the global banking system has turned into complete trash, with zero credibility.
Freezing accounts, sanctions, exchange of information, closing accounts for no reasons, this is what today’s banking system is. There is no more secrecy or trust anymore. So from this point of view, there is no reputation left to defend.