Guide element in OPF file for iBooks

Liz Castro says iBooks requires the Guide element in OPF file.

Then I read this, which says it's been deprecated.

Authors may include the

guide

element in the Package Document for EPUB 2 Reading System forwards compatibility purposes. EPUB 3 Reading Systems must ignore the

guide

element when provided in EPUB 3 Publications whose EPUB Navigation Document includes the

landmarks

feature.

http://idpf.org/epub/30/spec/epub30-publications.html#sec-guide-elem

Is it still required?