I've not seen this race format before i.e. top three to the final.
I couldn't see any reason for the recall either, perhaps indecision by starter? Usually, when I have raced, there would be an individual recall sounded if one or two crossed early. When this happens the transgressors number would be called and they would have to re-round the start marker. If too many start early a general recall would be sounded and the race restarted.
They can get amazing speed, they were hitting almost 30kts in 16kts of wind in rough conditions. My best on foils is about 21kts which, for me, can be scary in rough conditions. I'm comfortable at about 18kts.
In my Avatar I was doing about 14kts in about 8kts wind, which is close to minimum windspeed for foiling.