I use iPad Pro 2020 12.9", iPadOS 16.5.1 ("is up to date").
In the enclosed spelltest.afpub I have duplicated a Frame text box, and language is UK English:
I change that to German, and the wiggly lines disappear in the selected box:
I apply the style change:
But the rightmost box still has wiggly lines:
Doing the above with other properties, such as bold, takes effect immediately on update style, both boxes become bold:
Only if somehow