I'm probably 70+ oil extractions in on 617.952 engines using this...
...and sliding the plastic tubing into the dipstick tube and have never encountered a problem. Either I'm overdue for a fiasco or this advice is nonsense at least as far as the 617.952 engine is concerned. After a combined 450,000 miles or so, I'll comfortably and confidently continue on the existing course.

In re: "The dipstick tube doesn't go to the bottom of the pan, so what would you expect this to do?"

On the 617.952, the bottom of the dipstick tube is so close to the top of the oil pan that it is quite unlikely that one would be able to successfully wedge the plastic tubing between the two. Could it be done? I suppose. Can people abuse alcohol and/or narcotics and then drive? I suppose. Besides, if one did succeed at wedging the plastic tubing in place, one could simply remove the oil pan.

This all sounds like an anticipated crisis at least as far as the 617.952 engine is concerned.