Runway heading is exactly what it says - the compass direction or QDR when on the centreline.
"The compass direction when on the centreline". You don't really mean that, do you? I can be "on the centreline" with all sorts of different headings.
Seriously, I understand that's how
you interpret it (as does the FAA). I'm not seeking opinions, simply pointing out that the ambiguity exists.
SIDS in Canada tend to be runway heading to a given altitude, and can be quite entertaining at times.
Apart from the passengers, why on earth would anyone
want a SID to be "quite entertaining"? Wouldn't you rather it were "safe"? I can understand someone saying "it doesn't matter if you compensate for drift or not on this procedure because it doesn't make a significant difference". I can't understand any reason for saying "you must not compensate for drift because we want you to end up in a random place relative to the prescribed track".