There is the "eye" definition for the units, there's no knowledge about it on the Stranded website. I have an idea it could be for the range of when units see you, maybe?

Anyone know?

Have you double checked here?: https://www.strandedonline.de/s2_definitions.php
It has an 'eyes' definition. If it just says 'eye' than maybe it's a typo.

Note: eyes is how high the unit's main mass is.

No, eyes are used to set camera height on player. Might be used on other units just for some unfinished multiplayer functions.

it does both, because in debug mode you will notice that the semi transparent sphere that defines the unit collisions(or something like that) is higher up.