Wikitables set with a global alignment in style will show headers centralised on desktop and according to that global alignment on mobile.
Steps to Reproduce:
Set style=text-align:right (or left) at the wikitable declaration line. Check whether headers are right (or left) aligned on both desktop and mobile modes.
Headers show centered on desktop, and aligned right (or left) on mobile.
Being used to editing WP in desktop mode, I expect headers to be centered on mobile mode as well (unless specifically told otherwise). But I could also get used to the reverse convention: global style applies to all, including headers, which are easy to recenter with a row style, if need be.