Your friend is partially correct, but perhaps a bit biased towards Apple 😉
It is actually becoming very popular and works in over 97% of browsers, and some of those are starting to make it the default download format.
Apple, as they tend to do, does support it, but only since Safari 14, but then only when installed with macOS 11 Big Sur.
I haven’t investigated what would be needed to add it to kiwitrees, but may do for KT Nova.
I understand there are ways to convert them to “normal” jpg etc.