I'm assuming so. Apparently it's an angle that "invites" people to use the computers, but I don't think there's anything specific about 76 degrees that makes it better than, say, 73 or 82. As long as you can see the content from an average height, it should work. Most likely they just settle on that angle because it looked good to the store team that was staging the first store, measured it, turned out to be 76 and kept it the same across stores since then for consistency.

I believe the rumor is that 76 degrees is slightly uncomfortable enough to look at that it makes you want to adjust the screen, which in turn makes you more likely to try the device.

Yep this seems like it makes a lot of sense— and adding on, picking a measurement means that all of them can be the same (consistency, as you said)- having variation in the same row would look bad from a distance