Input Control and Buttons Focus Contrast

Hi All,
           Contrast ratio of at least 4.5:1 between text and background is
one of the primary requirements for WCAG2 level AA compliance.

https://www.w3.org/TR/WCAG20-TECHS/G18.html

But Can we have a ratio 3:1 for Input Control and Buttons focus contrast
based on
<http://goog_1899924365>
https://www.w3.org/TR/WCAG20-TECHS/G183.html

https://www.w3.org/TR/2016/NOTE-WCAG20-TECHS-20161007/G195 . If not for
focus what is this 3:1 ratio meant for?

Thank you,
Ashraf