Brunswick Blue

Why is the retired batter, a runner? The batter was out on strikes - never becomes a runner (by rule). First base was occupied with less than 2 outs in the OP.

LL Intermediate game (12-13 YOs) - I'm PU. Bases loaded; 1 out. Ball hit slowly between F1 and 1B foul line. F1 fields and comes home trying to get R3. Throw pulls F2 to right of home plate - foot now off plate. F2 gloves the throw and now (for whatever reason) tries to tag R3 In trying to tag R3 - F2 (quite inadvertently - but I know it doesn't matter) - steps on the plate R3 arrives at plate standing at almost the exact time that F2 steps on the plate AND attempts to tag R3. R3 (non-intentionally) in process of scoring runs into F2's glove and ball comes loose. I got R3 safe - as 1) ball must be controlled through a tag of the player or a base; and 2) "slide or attempt to get around" is not applicable here as it was a bang/bang play - and F2 was not waiting to make a tag. D - coach tried to argue the mythical must slide; and that the plate tag preceded the dropped ball. Did I get it right? Also - "waiting to make a tag" is a bit subjective - what do you all consider "waiting"? Thanks