I seldom get an accurate BP measurement at the doctor's office as they do not have the time or usually the training to do so. Any home monitor is going to be better. With the Garmin smartwatches often the center of training programs people want all their data in one place and this is behind the added functions in the watches and their increase in price and increase in popularity.
A key problem with the Apple watches is their short battery life which is a fraction of that provided by the Garmin watches. My Epix 2 has a battery life of up to 16 days. Compare that with up to 18 hours for an Apple smart watch.