I think there is few misstakes ...
18. is twice there.
Illithind Collony and Friendly Arms Inn.
Illithid Colony is nr 13, not 18. That being said, just like Act 1 I doubt these numbers mean much. In act 1 you could pick and choose to some extent where you wanted to explore first. Granted, some places would be more difficult than others at lvl 3-4.
As to the OP post/picture. Im really curious about Underdark vs overland. I mean can one go underdark/Grymforge, then choose mountain pass Gith Creche before taking elevator? How about after elevator, or would Gith Creche be locked off at that point? What about mountain pass, then underdark etc.
Or does one have to choose?