Undead Guide - Why do I have to do a few quests in Org at around level 14-16?

[reynbow]

The levelling guide suitably starts in the Tristfal Glades and makes complete sense.

Then it takes us to Silverpine Forest for... about 5 or so quests and then out of nowhere the guide tells us to take a zeplin to Orgrimar and run outside to The Barrens and pick up about 20 or so quests before it gives up on The Barrens and tells us to take a Zeplin all the way back to Silverpine Forest and pick up where we left off.

What....? Why?
I'm very confused about this... I'm sure there must be some logical reason but I can't figure it out.

[JDMiddleton]

The main reason the classic guide is so different from the retail guides is simply because the Zygor guides from vanilla were built around solo leveling. This meant that you had to do quests in a certain order and there were way less quests back in the day (Cata changed starting zones and generals quests quite dramatically.) So you have to hop around a bit with Zygor classic but in the long run you will not have to group up to reach 60.