In addition to the scale effect on accretion, as mentioned, there's also the scale effect on the aerofoil itself. It takes longer for the bigger wing to build that 3" ice shape, AND 3" of ice does more damage aerodynamically to a smaller wing. So smaller aerofoils get a double whammy in icing conditions.
Bingo...another true statement.
Now, lets look at
when it is prudent to use wing anti-ice, on a swept wing jet transport airplane.
IF you are going to use it, do so when the wing has no slats/leading edge devices extended, as....with many designs, the anti-icing is
far more effective when the wing is clean, aerodynamically (devices retracted).
NB.
Some might say...'well, if smaller aircraft use the three inch criteria, larger aircraft should use...more.
One aircraft manufacturer did just that...five inches.
Lockheed.
And, still found no anti-icing required on the tailplane.
TriStar.