There's an older parallel here for when #Mozilla helped #Google in their path to kill #RSS (note that this #XSLT is *also* about that) by removing the Live Bookmark feature. At the time, the excuse was that the implementation was incompatible with some important code changes that were happening at the same time, but the fact that support could be trivially brought in via extension showed that the issue there wasn't technical, but a matter of intent.