Grace note tuplets are an “exotic”, non-standard notation.
A group of 3 grace notes is often played faster than a group of 2, without any tuplet markings.
Since a grace note’s timing is only approximate, defining an X-number of undefined durations in space of Y-number of undefined durations is contradictory and could be confusing.
A much more efficient way to differentiate the speed of grace notes is using different rhythmic values.
A 16-note grace note will be faster than an 8-note grace note (but not necessary twice as fast).
Most of the time an exotic notation is just an eye candy, which only makes music more difficult to read.
If you can’t tell the difference between an actual performance of an exotic notation vs its traditional equivalent, it usually just cuts your rehearsal time.