In your opinion, is the situation described an infield fly?
Don't know, I wasn't there and this is something an umpire has to see to judge. There is a little bit more than just makeing a call that goes into this decision including things like knowledge or observed ability of the players on the field and wind conditions.
It is an easy rule to apply, so I don't know why umpires and coaches have such a difficult time with it. IMO, it is the easiest rule to understand.
Multiposts were required because the site wouldn't handle the size of the single response.
I can see that it would be possible for a fly ball to land on the edge of the grass in the outfield and still be called an infield fly. The dirt and grass are irrelevant to the location of the infield or outfield. Never have been, never will be. It is a myth. The infield is the area covered by the infielders. The outfield is the area covered by the outfielders. An infielder could be playing 30' beyond the baselines and it would still be the infield, grass, dirt, concrete makes no difference, the surface is irrelevant. Again, something defined in the rule book.
I am again confused. If it's not a pop fly and not a line drive, what is it? As noted, subjective. What is a hump-back about 12' off the ground? Is it a pop-fly or a line drive or just a fly ball. Too many people believe "pop" means it must rise high into the air and the rule does not require it be anything, but a fly ball and not a line drive, both of which are defined in the rules.
I'm confused by your statement. To me, "catchable ball" and "be able to be caught" are the same thing. Depends on your definition of catchable. The umpire is to judge an IF if the batted ball COULD be caught with normal effort by an infielder, pitcher or catcher. And that judgment is supposed to be made at the apex of the ball's flight. If a ball goes up over the IF and the umpire believes that is could be caught with normal effort and no one moves to make the catch, by the time is descends, is it still a catchable ball? Regardless, it is still an IF