Here is a side view of apparently the same model 627PC revolver from the article showing the lock tumbler still in place:

http://www.bang-inc.com/images/gunsg...lver.large.jpg

The tumbler is held in place by a spring loaded yoke that basically performs a locking ring function as well as being a detent for the tumbler.

It is probably unlikely that the parts would come loose and jam up the revolver but why invite the possibility? There is always enough potential for Murphy's law to mess things up.

Maybe Jerry Miculek kept the tumbler so the lock removal modification would not be too obvious to viewers from the side