Wow... much ado about nothing.
I'm in the camp that claims that a diametric true position is a legitimate control for the square hole and the slots. The FCF is locating the center of the feature to be within a certain diameter. Can the center be determined? Then why can't it be controlled to within a diameter? The orientation of the feature could be controlled by an angular block tolerance. Perhaps it was designed allowing for a circular tolerance zone, and a rectangular tolerance zone using the same tolerance would be too large. You may not be able to imagine a situation where this could be the case, but this would definitely be something to check out with the designer before casually ignoring the diameter symbol.
That said, I do agree that this is probably not the intent of the design, and is a poor way to locate the features.
It is a yellow flag to me when "old pros" fall back on their years of experience instead of using specifics in the standard to prove their point.