Maybe there’s a way to influence that - if someone knows maybe they can answer, I don’t.
I think using a show rule to apply centering is a good way to handle it, something like this
#show text: set align(center)
#(
box[1],
box[4],
box[6],
box[4],
box[1]
).join()
Or - I’m agnostic about how you solve the spacing issue, you can help yourself and define a “new kind of box” to make the repetition easier this way too, as an alternative
// #let cbox = x => box(align(center, x)) /* easy version */
#let cbox(body, ..args) = box(..args, align(center, body)) /* general version */
#cbox[1]/*
*/#cbox[4]/*
*/#cbox[6]/*
*/#cbox[4]/*
*/#cbox[1]