perennial runner beans

I just read an article which claimed that scarlet runner beans are perennial, even down to usda zone 4 if well mulched. Does anyone have experience with growing these beans as perennial in a colder zone? I did find another article which stated they were perennial to zone 7, which seems pretty reasonable. I so want to believe the zone 4 thing is real.....

I like to recommend scarlet runner beans because they are so pretty.

I have not grown them though from reading the forum I have found them to be perenial:

Joseph is in Zone 4B and says he has found some:

Joseph said, Only some of the plants had roots that looked like they might be perennial: 3 plants out of 100.

https://permies.com/t/25648/Scarlet-Runner-Beans-perennial#737577

I am in a warmer zone, so I can't directly answer your question. My experience has been that they do seem to be a perennial that gets stronger and more weather tolerant over time, in comparison to the first year or two. Perhaps it would be helpful to plant more types of runner beans than just the scarlett runners in case some work better than others. Personally I like these:
https://www.ranchogordo.com/products/ayocote-morado

I found them to be pretty sturdy plants. I tried the Sunset runner beans from Baker Creek, and they are pretty, I've also tried some white flower runner beans in the past but I didn't try to keep those multiple years. The vine seemed smaller on the white ones.