Did you tilt?

the tilt is used to triangulate incoming sounds to better discern the source.

I thought so too. The picture looks like it's more about the ears than the eyes.
- it's almost certainly both, you're right.

Do you even tilt bro?

I just realized I tilt my phone when something onscreen is at an angle

Your comment made me go back to look at the OP tilted. Then I realized the OP is already tilted and I too tilted it so it would not be angled without even realizing it. Then I realized why you posted this comment in the first place.

Don't human do that too? I sometimes even do it deliberately to indicate that I'm interested in listening to something another person is going to say, but maybe my body language is way off?

Yes humans do too, shows interest in something, though sublty more than a 45 degree tilt. Animals mostly do it to hear differently. though you probably also tilt your head to try and listen to something better.
- I guess humans do it as a sign of interest specifically because it indicates "I am listening closely."
Humans do it for different reasons. Our ears already do a good job of helping us determine where sounds are coming from vertically. Dogs ears lack some of the cool ways our cartilage works, they do this to introduce a difference in verticality between their ears.
(Or so I learned from Real Engineering’s video about the Apple AirPods I watched literally this morning on Nebula. It’s also on YouTube I think. Interesting stuff.)
I have two toddlers who do this during lunch time. Like, look at me and tilt their heads in an 45 ish degree angle.
Is that what it's for? I had a good friend from a small village in India and his grandad did that all the time, back and forth while he was talking. You're saying it helps with his hearing? That totally makes sense.
- I think india does a head shake thing, back and forth kind of head bobbly, that's similar in meaning to people in the west nodding in agreement. I've seen ones of videos talking about this so I'm clearly not an expert on the subject.

My neighbor’s dog has it figured out. It will keep its head straight, prop one ear up, and one ear down. And it’s even goofier when they and I lock eyes.