Thanks, Mike,
I went to the Addendum and the explanation given confirms what I'm suggesting. Here is what I copied and pasted: "If prior chips don’t cover the call AND are either left alone OR fully pulled back,"
So I think the issue you're raising is that
technically chips out in front of a player from a previous bet should not be retracted by the player. However, in reality that happens all the time. Players will reach out, add a chip(s), take one back... in order to get their bet right. And most of the time it doesn't create a problem, the dealer is following the action and understands what the player's action is. Hence notice the key redline change to Rule 46-C
"if new chip(s) are added silently and the bet is unclear to the house". SO, the guidelines in 46-C are really intended only for those few outlier situations where there's some confusion about what the legit bet is based on the player's action. It's not intended to be invoked everytime a player adds to the prior chips and the action is crystal clear.
The more important parts of Rule 46 are really A and B which do apply to every situation: A, that a player with prior-bet chips in front should verbalize action prior to putting out new chips AND B, that pulling back any or all of the prior chip(s) binds the player to at least call. In the past some players had manipulated prior chip(s) in order to get a read then throw them back out and fold, that was ruled illegal at the TDA Summit in 2015.