Yeah, iOS will try to automatically detect phone numbers in web views. It can be annoying sometimes if the web page author doesn’t take that into consideration.
And yet in some crazy parallel universe, content authors choose to tag telephone numbers as such to make them clickable, rather than having to tell a browser not to incorrectly interpret text.
RFC-5341 defines "the tel URI for telephone numbers" and is dated December 2004. The first iPhone was released June 2007, so there was already a way of marking phone numbers well before day one.