It is actually easiest to think of it this way. If the FLEX is playing defense, then no matter what other job that position assumes (i.e. batting, running), then that player has never been subsitituted for. The FLEX's primary job is to play defense.

The DP's primary job is to play offense, so, if the DP is playing offense, it doesn't matter what other job that position takes (playing defense) they are still not substituted for.

Now, if either the DP (offense) or the FLEX (defense) are not doing their primary jobs, they have been substituted for and are entitled one re-entry.

And we have now successfully hijacked this thread. :D

I guess that's rule 4...

Not really, I'm the OP and the situation was apparently caused by confusion regarding DP/Flex.

I.Basics
DP/FLEX must be known (shown on lineup) before the start of the game and the PU must track all changes. FLEX must be listed on the lineup in the 10th spot, DP anywhere in the other 9 (batting order) spots. Eligible players may substitute for the DP or for the FLEX.

II.Provisions
1.DP starts on offense, FLEX starts on defense.
2.If not in starting function, not in game.
3.DP and FLEX cannot be in batting order at same time.
4.FLEX can only bat in the DP slot.
5.DP and FLEX can play defense at the same time.
6.In #5, the player not on defense still bats.

III. Comments
DP/FLEX switches change the number of players actively in the game,but do not change the batting order and are not "substitutions".

DP/FLEX switches are not "substitutions", but if either leaves the game and returns, that is a reentry.