One further advantage of shooting with both eyes open is it takes more muscular effort to keep the non shooting eye closed than to keep it open. Why waste energy? This particularly applies to match shooting, as I well recall when competing in 60 shot 10 Meter competitions. One of the advantages of match shooting glasses is they blank off the non shooting eye to reduce peripheral vision and aid concentration - they also enable both eyes to be kept open throughout.
John M
Currently looking for Baikal Makarov pistols with the following prefixes to the serial number: 98, T01, T09, T21, T22
Prefer boxed or cased but will consider loose examples too.