In the window for one handed axe expertise there is a spelling bug.
It says “When using a Axe:”, should clearly be “When using an Axe:”
I can confirm this is also the case for the newest PTR.
You should report this as a bug. But that forum only exist on the US version of the forum, here are the links. Notice they are different for console and PC 
PC: https://us.forums.blizzard.com/en/d4/c/bug-report/7
Console: https://us.forums.blizzard.com/en/d4/c/consoles-bug-report/11