True Position for Multiple Features

In this Question Line video, Jason walks through an example that has one feature control frame controlling position for multiple features. He discusses why this is an allowable practice and identifies where this is practice is outlined in the ASME Y14.5 spec.
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[@Layout5520]

Maybe a dumb question, but why do the reference a plane that is not applicable to the true position? There is no call out for perpendicularity. I am referring to Datum A.
Thanks
Jim

[@sponcheyanderson3021]

I am also confused to the term "perpendicularity" and yet a lot of designer use positional tolerance and assume hole is perpendicular. This is especially true when designer use "MMC at 0"