FED Case Play 8.2.10 Situation A
 

With no outs, R1 is on first. F9 intentionally drops a fair fly ball hit by B2. R1 advances and is (a) tagged out, or (b) reaches second or third base. Ruling: In (a), R1 is out. In (b), it is a legal advance and B2 is safe on the error by F9. (5-1-1-l; 8-2-10)

I don't understand this ruling. An intentionally dropped ball is an immediate dead ball (per 5-1-1-l), therefore, anything that occurs after that never happened. R1 should not be out. Also, the advance of R1 in (b) never happened. R1 should be put back on first (8-2-10). Even the rules referenced don't support the ruling. What am I missing?

5-1-1-l: an infielder intentionally drops a fair fly, fair line drive or fair bunt in flight with at least first base occupied and with less than two outs. EXCEPTION: Infield fly rule (7-4-8, 8-2-9).

F9 is right field, not infielder.

Yep, I missed that!
 

I was thinking infielder. When I discussed this with a fellow umpire this weekend, he pointed out the same thing!