get-help issues

I'm confused.

Overview
I've written a basic cmdlet called Write-Hello. It more or less does what it says, and also contains help information. I run the script to load it into memory. 

Issue 1
If I do WRITE-H<TAB KEY PRESS> it uses tab completion as i'd expect it to 
If i do GET-HELP WRITE-H<TAB KEY PRESS>, there's no tab completion. 

Issue 2

If i do GET-HELP Write-Hello, it successfully displays the help information contained in the function 
If i do GET-HELP Write-H* it does not display anything

Built in commands do not have these problems.

I'm stuck with what to do next.