ASA 12u rec ball, no outs, R1 on 2B, R2 on 1B, B3 hits a pop-up into the Bermuda's Triangle between F1, F4, and F6, shading more towards F4. As the ball reaches its apex, F4, playing deep, gets the deer-caught-in-the-headlights look and doesn't move towards it. F1 turns around and points at it and is probably expecting F4 to run up and catch it. F6 is making a valiant effort to get there but is obviously too far away. The ball falls harmlessly between the 3 players, and all runners are safe. I didn't invoke the Infield Fly rule because I didn't think any infielder could have caught the ball with ordinary effort. Had this been 14u or the players involved a bit better skills-wise (a more competent F4 would have been able to catch the ball), my call would be different, but I didn't think any infielder at that moment could have caught the ball with ordinary effort. My assignor/mentor was there, along with a couple of other guys that umpire, and they thought I should have called Infield Fly regardless. Looking for feedback. Obviously, HTBT, but does the rule allow for some nuance like this, or should it be called regardless of the level of ball being played?