Gregs, you make it sound as if MB has to be forced to perform repairs under warranty, You might have said they will be pleased to resolve a catalytic converter issue for you. You may not have worked with customers in the past..... LOL
I've worked in a customer-service capacity of one kind or another for most of my life.
However ... I don't work for MB and never have (and it's unlikely they'd hire me after posts like this, lol), but after reading probably 200 posts on the same basic topic, most people assume either there is no warranty on the cats or the dealer will fight them.
Thus, I've simply reached the point that I spell it out more definitively, that the dealer is required to, which cuts down significantly on repetitive posts seeking clarification.
For example if I try your tactic, the response comes back, "well, isn't the warranty expired it was only four years" and we go around again, eventually getting basically to what I posted in this thread.
Moreover, there are several threads on this topic wherein someone comments that they went to the dealer for this and were treated with less than exemplary service...in some cases it was more of an attitude of grudging complacency and some folks were required to pay for some mounting hardware or other miscellaneous things in order to have the cats replaced "for free".
Dealers vary, but IMHO based on what I've read in this forum, nothing could ever convince me to represent that every dealer would be pleased to resolve a cat warranty issue. (Don't get me wrong, I'm sure there are lots of great dealers, and they more than anyone are probably less than thrilled with MB's cheap cats, but...)
Of course that changes at 8 years one month or 81,000 miles, because then it's a huge chunk of profit for the dealer. Not that I'm cynical, of course.
Take care and enjoy the ride,