Anyone know the current state of shield bashes?

I created a quick iconic to do some testing... and if what I found is correct, there is good news and bad news.

The good news is it does seem the feat is working as described. From what I could tell, I was getting bashes 20-25% of the time. Considering the feat gives 20% and the pdk shield gives 4%, that seems about right.

The bad news.... when I took the Stalwart Defender "Shield striking" enhancement, it didn't seem to change anything. As far as I could tell, I was still getting the same 20-25%. Additionally... I checked a bash vorpal, and it didn't mention anything about the knockdown. Now, this was a dummy, but I did get a message about vorpal immunity from the pdk sword.

Is this the correct current state of Shield bashing? Is the feat finally WAI yet all enhancements are simply busted?