Good you figured that one out.
This is a known flaw (and not the only one) in the specs over here.
All broadcast here (SD as well as HD) is XDcam style, but to annoy as many people as possible, some geek wrote specs as difficult (and as it turned out flawed) as possible, without simply stating ‘make XDcam and all is fine’.
Watch out for burned in subs as well, they are specced to have illegal (super) black outlines, that might get your work rejected for being conform specs.
(I recently had a huge fight with a broadcaster who send me wrong leader / trailer material. Parially wrong field dominance (so, not fixable), beserk audio levels, fade out where there was none intended, out of spec video levels.)
If you need to do commercials, contact me as I’ve got some nice tools for that.
Bouke
http://www.videotoolshed.com