Steve,
I look at it a little differently. The rules regarding interference use two different key phrases: "in the act of fielding" and "attempting to make a play". Nowhere in the rules are either of these phrases defined. The text of the rules are ambiguous as to when exactly the fielder is "protected". As you know, this is not the only ambiguous thing in the text of the rules. So, we turn to interpretation manuals to clarify the ambiguity.
Both J/R and the MLBUM suggest that the protection afforded a fielder during "the act of fielding" a batted ball continues through his subsequent attempt to make a throw after gaining possession of the ball. It doesn't strike me as "adding" anything other than clarity to the text of the rules. It also strikes me as entirely consistent witht the purpose of the rules regarding offensive interference.
DG,
I know what you mean. Maybe it's just catcher's who aren't protected from "malicious contact" - pitchers certainly seem to be.
JM