It seems that you are correct. I did a little internet detective work and came up with this link and information.
"...calling Tyvek just to be sure and they said the house wrap is "non-directional," so it can be installed anyway you want".
I found this link and info by googling the question, "is tyvek house wrap directional". The above partial quote is from a message board with the header / question for discussion, " House wrap installation, print toward house ok"?
Thanks for the link to the hammock forum.