In the beginning of lesson 13, 4 rules are given. The fourth rule states that, for purposes of blending, woods of the same type should not play dissonant intervals. Strangely, the 5th is included as a dissonance.

But even stranger, he breaks this rule only 2 examples later, when demonstrating voicing a chord using overlaying (bassoons play at the interval of a 5th).

This leads to two possibilities:
1) The 5th was mistakenly listed in this online version as a dissonance, in which case its use in the example doesn't break rule 4
2) The 5th should be treated as a dissonance within the musical subworld of woodwind orchestration, and RK violated his own 4th rule within a few breaths of laying it down.

Either way, something ain't quite right. Can anyone shed some light on the situation?

Much appreciated,