Hi,
According to the La Crosse support techs, they haven't had the unit long enough to really know how it works! They said that if it works the way other units do, it will sample several times (say every 4 seconds) during the interval (17 seconds per specs) and then send the highest record sampled (for gusts) and the average of the record samples (for average wind speed) to the hygro at the end of the interval (17 seconds per specs); the hygro then transmits to the base unit. However, my base actually receives updates from the hygro every 13 seconds and updated data is received from all 3 sensors each time (so actual performance seems to be better than the stated specs!)
As a side note, the specs say the wind speed resolution (that is, the step between each measurement) is .22 mph. That is true for my average wind speed measurements, however, my gust speed measurements demonstrate a resolution of about 1.34 mph, which is also what the La Crosse support techs are getting.