18/6 has never done anything to my BP, I've been doing it for 10 years.
I suspect the biggest impact was trying to lose weight and changing your diet. In my case changing my diet has noticeable and immediate effect to any physiological metric than any other "trick".
I didn't change composition of my diet much back then, but I noticed that on days when I fast longer, my BP goes even lower. I could probably fast myself into lightheadedness now on Concor (not that I want to).
People are fairly diverse, so different reactions are to be expected. Our gut microbiota is diverse, too.
I also noticed that even slight amounts of alcohol (1 glass of wine) are visible on my BP for about 24 hours after. An increase of 5-7 points.
I suspect the biggest impact was trying to lose weight and changing your diet. In my case changing my diet has noticeable and immediate effect to any physiological metric than any other "trick".