I’ll use a concrete example. The arrangement of these items look perfect to me:
I think they look good to me because they are almost perfectly aligned and the distance between each item is similar.
This is a modified version of the same items:
They are shaped as a heart.
For a design point of view, are both versions equally well-arranged? If not, what are the factors that are making the second one look less well-designed? (e.g. symmetry, distance, size.)
The humans unintentionally all the time try to find patterns that give to the objects some relation with the already noticed. In your first image it’s easy. Paper is rectangular, the arrangement have lines that are parallel with each other and the paper edges. Rectangularity also is a familiar relation. The subgroups all have an easy to see internal reason to exist. The space is evenly filled. => It’s easy to see some order existing.
The second example has not any reason, why the shape of a heart is formed and everybody surely do not even recognize the heart. This changes to be ok if the reason (=easy reference) would be obvious – other, more clear heart or textual content or more likely, the both.
Here’s an easy to see reference that gives the reason – a servicing plate.