Unable to change a single value of an array property - aka Position|Scale

I'm trying to replace just the xPosition property while retaining its yPosition for multiple layers.

Current constructs are such that all selected layer's yPosition adopt the yValues from the first selected layer. 

The result is really strange and I'm wondering why would this be part of the product's design. If I wanted both X-Y position values to exactly that of another layer, I would copy paste that layer's position property - so, there's already an intuitive way to accomplish this. Hence, writing in/over just the xPosition value should allow for changing just the xPosition value.