Today, we are excited to announce the availability of OWA for iPhone and OWA for iPad, which provides even more value to organizations on any Office 365 subscription that includes Exchange Online. ...
Updated Jul 01, 2019
Version 2.0
Blog Post
Kevin M,
As per the official App release page, https://itunes.apple.com/us/app/owa-for-iphone/id659503543
itunes.apple.com/.../id659503543, you need at least iPhone 4S. The part that you've quoted from Office 365 Technical blog post seems to be incorrect.
http://blogs.office.com/b/office365tech/archive/2013/07/16/owa-for-iphone-and-owa-for-ipad.aspx
blogs.office.com/.../owa-for-iphone-and-owa-for-ipad.aspx
Pasting here the full requirements from official App release page:
Requirements: Compatible with iPhone 4S, iPhone 5, iPad (3rd generation), iPad Wi-Fi + 4G, iPad (4th generation), iPad Wi-Fi + Cellular (4th generation), iPad mini and iPad mini Wi-Fi + Cellular. Requires iOS 6.0 or later. This app is optimized for iPhone
5.