Not wrong at all - negates the need to open up and douse them in cold syrup midwinter, but you need to really knock back the varroa at the end of the summer to ensure healthy winter bees, you can do this using OA by doing three or four successive vapes at five day intervals to cover the varroa brood cycle
Yes above is 100% correct autumn treat for a healthy colony and healthy winter bees 1x winter to kill anything you can for reduced numbers the year/season ahead