On that third link, I can translate the relevant French text:
Dimensioning should be avoided in axonometric views. If it is necessary, the same rules as those used for orthogographic views should be employed.
To amend what I succinctly replied at the end of my lunch break: I don't think dimensioning axonometric views is considered an "official" convention in either of the existing norms (ISO, ANSI...), but it is commonly used nonetheless. And yes, the dim extension lines should be parallel to the XYZ axes.