No physician should (and I expect would) diagnose hypertension on a single office-based blood pressure measurement. We suspect it based on the office measurement and then confirm.

I last worked in primary care back in 2016 but even back then we would either do multiple visits or ask the patient to check multiple times at a pharmacy (or at home if they could afford a cuff).

24 hour ABPM is the preferred method for diagnosis as you stated but has limited (albeit growing) availability today.

Fortunately consumer health-tech advancements has resulted in cheaper accurate BP cuffs but this is a recent-ish phenomenon.