Not sure how the author comes to the conclusion that opus isn't widely supported.
Opus is supported in all major webbrowsers and natively in modern Android systems. I'd call that widely supported.
Opus is supported in all major webbrowsers and natively in modern Android systems. I'd call that widely supported.
Not supported in Safari. I guess the reason is that iOS devices don't have hardware encoder for it and Apple doesn't want to compromise battery life (maybe marginal issue with audio, but big issue with webm).
I rather think that Apple doesn't like the idea of royalty-free codecs which would make it easier for free operation systems to support multimedia on the web. AAC helps to keep you locked into macOS or Windows, because it works out-of-the-box there (in contrast to Linux distributions like Fedora).
I wouldn't call a technology that's only available to 63% of your users 'widely supported'.