For example, double-clicking on my Mac would zoom the document to 67% giving 1:1.
The zoom level needed for the 1:1 view is also not usually a whole number, which means you probably won't even be a able to plugin 67% to get an exact 1:1.
I can get the 1:1 zoom level via scripting in CS6, and for my 27" iMac it's 66.055047793651—66% doesn't work.