"if it were an actual problem"
I have three verified cases of unsupported magazine extensions getting knocked off guns and damaging the gun's magazine tube threads.
Case #1 was a small town police chief answering an armed robbery call at a bank (false alarm).
He bumped his Wilson extension on the car getting out.
The extension was blown off with such force, the opposite window was shattered.
The gun's magazine threads were damaged, needing a trip back to Remington for replacement.
The chief told me how sick he felt to be possibly facing armed bank robbers with a 6 shot revolver, because he failed to install a clamp as several people told him to do.
Case #2, a local doctor who kept a Winchester 1300 with a Choate extension in the bedroom.
He opened a closet door and knocked the gun over. It slide down the wall it was leaning against and landed on a low wooden chest.
The extension was not knocked completely off but was bent out of line and "hanging by a thread".
The gun's magazine threads were deformed and ruined.
He traded the gun off, the new owner installing a new magazine tube.
Case #3, I personally saw.
A police officer at a training session was shooting a stage where he kneeled over a table simulating a car hood. He would then stand and step over to a PPC barricade to simulate taking cover behind a wall.
When he stepped over to the barricade, he bumped the Wilson extension on the barricade, knocking the extension off.
The extension and spring shot a considerable distance down range, and shells were scattered all over the line.
The gun's threads were damaged and the gun required a trip back to Remington for a new magazine tube.
I actually saw the incident and the bump was NOT a particularly heavy blow.
As is always the case, people are free to do as you wish, but knocking magazine extension off guns DOES happen, and more often than you think.
There are no really good reasons NOT to use a clamp, and several excellent reasons you SHOULD.
Make your own choices.