...I would assume the latter. I think you would want the oil feed to be close to the bottom, where the metal to metal contact area would be, when load between the push-rod & spring begins. Every thing is pushing "up" on the rocker arm. But if there's something about the groove itself, that should not be in the load area, then I'd like to hear that reasoning. Might be something like the "Cutter Cam" deal.
...fwiw 440's are at the bottom.
...PS. but the upper position might be a Hemi oil squirt to adjuster cup/ball oiling for proper index of the groove.
...EDIT: just checked, & the groove goes down & there's a squirter hole up top.