Tab is typically used to move from element to element, not to change the state of the element.
Space is generally used for simple binary state changes of the kind you described.
As an example, assume the user is focused on the first element of a form with a two-state switch as the fourth element defaulted to state 'A', the switch can be switched to state 'B' by hitting Tab Tab Tab Space.
I believe this can be disabled in cases where you might actually want the user to make a 'positive click' rather than casually tabbing through the form.
Most accessibility requirements include the provision of facilities for users who cannot operate a mouse which would normally be covered by the Tab or Space functionality. Turning these off is almost certain to harm your accessibility rating. It's probably not mentioned in Material because it's inclusion is presumed as a standard accessibility facility.