I can appreciate this outlook, but I still worry about "just wasn't available when the code was written".
Code rot is very real for websites, and I worry that in the quest to do things 'right' Chrome is undervaluing the incremental harm done by every change. I don't think this action broke the web, but I'm wary of the idea that breaking changes can be casually blamed on the people who didn't update fast enough.
Change is bad, inasmuch as it makes new work for maintainers and harms user experience where maintenance isn't prompt. It's often necessary, but there ought to be an open discussion about timeframes and impact before a change happens. In this case, the discussion largely happened after the fact.