The variability of readings is notorious. I have a key saying: if it’s EVER normal, it’s normal. Period. All that stuff about atherosclerosis etc is not valid if the blood vessels can be normal for just one day.
I agree we should never diagnoses a BP tendency without many readings over months (diet is the answer, anyway).
But what we are talking about here is machines that can give one reading high one minute and then low later.

I have a patient who is severely hypertensive and who refuses conventional BP drugs becauser they make her ill. In January her BP was 187/106 and when I took it in February, it was 200/100. At that point I insisted she see her GP who gained a reading 180/100. It made me doubt the accuracy of my machine.

I find that if I take my own BP and then take again immediately afterwards, there can be a marked difference both in systolic and diastolic readings, the second reading usually being significantly lower. However medical literature reports that definitive BP assessments based on single readings or even a handful are known to be generally very untrustworthy and the usual recommendation appears to be to continue to take several times over a relatively long period of time to reach a trustworthy assessment of what is happening.

Of course, many of us do have serious doubts as to some of the practices of the drug industry, but I would only want to come to a definitive conclusion following research which should be relatively easy to conduct.