Bob,
Grammatically, it is an "or." (Unfortunately, grammar does not appear to be an area of focus in the manual, as there are several questionable items!) Subpoints A & B both indepently complete the phrase, "This occurs when:"
"Using this description..." refers to Article 8 as a whole. Reading this as "a" or "b" is also consisent with the rest of the manual. For instance, I just thumbed to 4-19-5, "A technical foul is:
a. A foul by a nonplayer.
b. A noncontact foul by a player.
c. etc...
The bulleted items (a,b,c,etc...) each independently complete the phrase with the colon (
. I'm being anal retentive here, but grammatically, you must read each of these items as "or". I further believe this is clearly the intent of the rule. Swinging the elbows in a dangerous manner, whether or not anyone is nearby, is intended to be a 'T'.