[greymule]

The "comment" does equate taking a "flying start" with failure to retouch:

7.10 Any runner shall be called out on appeal when—

(a) After a fly ball us caught, he fails to retouch his original base before he or his original base is tagged;

Rule 7.10(a) Comment: "Retouch," in this rule, means to tag up and start from a contact with the base after the ball is caught. A runner is not permitted to take a flying start from a position in back of his base.

[So what if the runner took a flying start, touched 3B, ran a few steps, then retreated, retouched 3B, and proceeded to home plate? By rule, he did retouch, unless his having taken a flying start somehow disqualifies him from later tagging up on the play.]

I never thought of it this way, but it's also an appeal if the runner overruns 1B and fails to return at once. I always assumed the ump could just call the runner out for dawdling, but apparently the defense has to call it to the ump's attention.