It seems like the cur­rent Soft­ware Update nul­li­fied my tweak (YMMV). I think this might be help­ful as most of the results showed only how to “dis­able sleep when the lid is closed” vs. dis­abling wake on lid open.

Any­ways, to do so, do the fol­low­ing in your Ter­mi­nal (Appli­ca­tion > Util­i­ties > Terminal.app):

Check cur­rent state (i.e. “lid­wake”):

$ pmset -g

Dis­able it:

$ sudo pmset -a lidwake 0

Or put it back to nor­mal (re-enable):

$ sudo pmset -a lidwake 1

Check the cur­rent state again to ver­i­fy (i.e. “pmset ‑g”). You should­n’t have to restart. I hope that helps. Would’ve saved me a cou­ple of min­utes for sure.