At Google yes, you would be expected to fix everybody. This will also give you exposure to client use cases and form a good basis for arguing your change is saf

At Google yes, you would be expected to fix everybody. This will also give you exposure to client use cases and form a good basis for arguing your change is safe, necessary, and correct. The idea that clients can run on the old library forever is a nightmare, especially for security-relevant changes. When I see a binary built yesterday I want it to contain yesterday’s code, not a copy of libpng 0.1 from 1996.