Very surprised to see a bug get patched in putty but says OpenSSH won't fix. Anyone reading this with the kind of background who can comment on that?

If I read the report correctly, this is a protocol level issue. The report lists a potential client side fix, but it’s not without problems and includes the following sentence regarding openssh: “ The developers of OpenSSH are not planning to change the behavior of OpenSSH regarding this issue, because of the aforementioned drawbacks. ”