It's also not people who have office jobs, or even jobs specifically in industries where this is very common. At $workplace, managers have 1:1s with their reports basically weekly or bi-weekly, directors with their reports typically monthly, VPs quarterly if they have time. There are tons of 1:1s happening and while some dislike them for various reasons (waste of time, no power to actually change anything, inefficient to discuss a bigger topic with 1 person at a time then have to do that multiple times, etc), I've never heard anyone talk about or suspect that anyone has felt weird about a 1:1 being between two people of different gender. It's a 100% normal part of working at $company, so if we ran the same poll as in the article, I'd be very surprised if it was more than a couple % on each side in the "inappropriate" or even boarder line camp.

Fwiw, all the small rooms used for 1:1s, and all conference rooms for that matter, have at least 1 narrow (but usually wide) full-length window.