Walking bass transitions

Hi Todd,

I am slowly going through your first "Walking bass" video, and at some point you state a rule for transitions: half/whole step above or below, quarter up / fifth down, octave up/down.

What's the rationale for this rule? For instance, if I need to go from Bb to F, what would be the problem with playing ..13/1... ? Is it because the harmonic change would not be obvious enough? Any other reason?

Thanks a lot for any hint,

Bruno