I don't think you're right. When MS Office started using the new formats it was considered a breaking change. I think you're too fixated on one point of view.
This is probably because disruption occurs when an old document is successfully opened by the new application, changed and then inadvertently saved in the new format.
In the predominant software culture, we don't regard that as a "breaking change". Breaking is when content created with older versions of software doesn't parse under newer versions.