I disagree. "contains" might be a nice name, but if it breaks a significant number of websites and forces many to have to update and fix websites that have worked for years, then a simple rename is a fantastic solution in my opinion.

This isn't about being "right", it's about finding the best solution to the problem at hand, and a solution that breaks things but is "technically correct" is worse than one that doesn't break things but has a slightly wonky name.