Reported via web feedback form:

One additional info I'd really like
to see for each core function is the OpenGL version when this function
was introduced. If a core function was promoted from an extension, the
extension name the core function is based on would also be nice to know
(even if the semantics might be different from the extension function).
This would enable developers who have to deal with an old OpenGL core
version to find a suitable extension that does what they need.