So I couldn’t get the glitch to work (currently testing on Overgrowth). Or really I couldn’t get it to work until I jumped into a tree. After that it worked on command.
Selecting a gear item now would cause the glitch to work. However I cannot get the wrist launcher to cause a half cloak.
I still can’t get it to work with the wrist blades and plasmacaster though. However I did note that if you select either of those two items and switched back to the weapon you’d been carrying prior you’d remain in cloak fully.
Edit: There’s a delay. Cloak works fine for the first ten or so seconds and then fails. So this is something afflicting Predator as a whole rather than anything in the loadouts.