Mary,
An interesting comment from you above.
If it really was "controlled" as effectively as you think it was that day, why didn't their ATC question your call sign as to why the r/way change hadn't been acknowledged ? Seeing as they were already exchanging positional RT stuff with you and knew your were taking steps to remain #2 to the small 'planes.
Ergo it wasn't quite so controlled as even you fondly thought so as ever it's back to the PIC in more ways than one - precisely as you have explained.
Ergo, don't trust any system even if 'it should be' i/c.
mike hallam (grass strip operator England)