Hook-Theory 4.2 Pre-Cadence Chord utility ranking?

At the end of section 4.2 there are several review questions of which one is “Rank the basic chords chords I, ii, iii, IV, vi in order by their utility as a pre-cadence chord.”

I looked back through the all the sections of Book I up to this point and the only reference to pre-cadence chords is in 4.2, but it only covers chords IV and ii.

Given the information available from the book up to this point, I would think that the ii would have more utility as a pre-cadence chord than IV because IV can only act as a pre-cadence chord to V. iii can only act as a pre-cadence chord to IV since vi is not a cadence chord, so I would think it doesn’t have much utility. I would (apparently wrongly) think the I chord has limited utility as a pre-cadence chord since playing it right before a cadence chord seems like it would lessen the effect of the cadence chord’s pull back to I, since you were already right at I. I did see that Tom Petty’s “Free Falling” uses I as a pre-cadence chord and it does sound good, so why does this work? Looking at previous examples I see vi being used as a pre-cadence chord to both IV and V so it seems like it would be ranked just after ii and before IV.

The actual ranking was “IV, ii, I, vi, iii,” but no reasoning was given for me to learn why these are ranked this way. Can someone please explain this to me so I can improve my understanding? Why is I a stronger pre-cadence chord than vi? I understand that iii is considered the “least flexible” chord of the 6 we’ve covered so far, so I can understand why that one is ranked last. I understand that IV and ii are the most used pre-cadence chords, but what about them makes them have the most utility in this regard? In a similar vein, I understand that IV has more utility overall since it can be used as a cadence chord, but why does IV have more utility than ii as a pre-cadence chord since it presumably cannot be used as a pre-cadence chord to itself?