I think the question has a lot to do with the user's technique also,
It would be interesting to know how many people think 1/focal length/1.5 is acceptable without shake reduction to hand hold a shot. Chances are, the same ones who say yes will also say higher stops gained here .
I took this shot in the linked post at 1/40 using a 510mm lens (1.7x AF TC on K300F4)
https://www.pentaxforums.com/forums/1056405-post7.html
This is extreme, 1/19 over the rule of thumb for non shake reduction and hand held and more than 4 stops. I will admit, this is very steady, but SR does deliver along with good technique. My typical experience is 2-3 stops is extremely reliable, 3-4 is typically possible, but 4 or more is possible.
I would also be willing to bet I can hand hold slower than the 1/FL/1.5 also