Over having the manager serve people? Do you have some reference that explains what you're referring to?
In practice, if the manager sees that server X often/always calls yellow on group Y, it becomes the manager's job to educate, train, or fire server X.
The problems with the described practice are pretty apparent if you've ever a) worked in tipped food service or b) been black.
And that wouldn't have to be a consequence of this policy. It would, however, require the manager to be as prompt as the server. This should be possible to do if they're paying attention to the issue, because the manager should be handling far fewer tables than a server.
http://articles.latimes.com/1994-05-25/news/mn-62027_1_civil...
Alas, the actual examples aren't fully enumerated (to the tune of some 4,500 complaints). The syntax of "slow service" in the cited examples is in seating customers.