Why NOARCH packages aren't available on all architectures?

From: Yuri <yuri_at_FreeBSD.org>
Date: Fri, 05 Aug 2022 01:51:29 UTC

When I look at the xsimd package's Fresh ports page 
https://www.freshports.org/devel/xsimd - it shows that xsimd package is 
available on some architectures but on others.

For example it isn't available on FreeBSD:13:armv6.

Shouldn't packages which are NOARCH be equally available on all 

What causes this not to be the case?