Interesting. I did not even know that extended versions were available.
I have an XD-9SC with a stainless slide that I love.
The first time I fired an XD at the range (not mine, but a rental gun I was testing), midway through the first string, I squeezed the trigger and...nothing.
I actually thought there was a breakage or malfunction for a minute.
Nope.
The gun was functioning exactly as designed - the web of my thumb had backed off the grip safety just enough for it to engage.
I was not new to grip safeties, as I have owned several 1911s in my time.
Now, I always make sure I push my thumb very far forward with this gun, to ensure positive disengagement of the GS.
Sorry this isn't the answer you were looking for, but you get a free thread bump at least.
Tag for my own curiosity.