Everyone is surely welcome to think whatever they want. However, don't completely dismiss the possibility that our friend MMC could have been wrong. One of his last writings claimed that choke is unnecessary, a rather obvious monthly column filling, piece of silliness.
The only way to prove it would be to take two identical guns, always closing one by the thumb sneaking method and always closing the other by the normal, factory recommended way, shoot a few hundred thousand rounds, over a 100 years or so, always keeping both clean and freshly lubed, and see which one gets loose first. I'm happy to take the recommendation of most, if not all, of the manufacturers. That is, to close it (not slam it) respectfully, with your thumb off the lever, allowing the bolt to seat properly.
Always a fun topic which probably never changes anyone's mind.
P.S. Just re-watched an excellent tape called "Wingshooting", featuring MMC and the late Jack Mitchell. Michael was shooting a Beretta O/U. He closed the gun 50 times, never once holding the lever. In nearly every closing, he closed it with his trigger hand on the butt, a practice he learned from Jack Mitchell, a wonderful instructor.
So much for the value of what he wrote.
If one were to take the time to read the entire McIntosh article--or at least that part focusing on chokes--one would find that he is addressing UPLAND HUNTERS in particular, as in: "For upland hunters, choke now is more bane than boon." When you consider the research done by Tom Roster in his CONSEP workshops, it's hard to disagree with that point--for the MAJORITY of upland hunters. Roster found that about 2/3 of the shooters he tested (something like 20,000 total) could not hit half the crossing clay targets at 20 yards. If you don't shoot any better than that, any choke at all is a hindrance rather than a help. And if you haven't looked at a cylinder patter on paper, at 25-30 yards using modern shells, you'll likely be surprised by what you see. Certainly, choke can be of value to hunters who are capable of hitting birds reliably at 40 yards or more. But Roster's tests showed that such individuals are a very small minority.
As for closing a shotgun with one's trigger hand on the butt . . . I've heard of that before, but I don't think I've ever actually seen anyone do it. Even at fairly large sxs shoots . . . although I'll have to remember to watch closer in the future. I tried it with a few of my guns. Works quite well with an old Parker, which opens and closes very easily anyhow. Not so well with guns that "resist" closing a bit more. Maybe, if one were to get used to the different application of leverage . . .
