That's how Disney does things for films, too. For Luca, they traveled to where the director grew up (like 6 people) for only a few days. I read about this and watched a featurette - they basically spent all of their time just taking in the sights, the sounds, the textures, etc, in Italy. They captured some underwater footage in their time there.
When they tend to do these research assignments, it's all about that type of stuff and really taking in the area and taking lots of photos, videos, and even sketching some of the textures to remember them by. They want to capture as much as possible in the area they are researching in the limited time they have.