This has been confirmed as a bug and will be fixed in a future version of Mosaic.
The AMENDEMPSTATUS system function is intended to let a worker edit an employment status that has an end date in the past, as long as it was updated at least a day before they access the screen.
The edit icon should appear for workers with the correct permission when the employment status has no end date, has an end date in the future, or was updated on the same day it's being viewed.
We'll update this article once a fix becomes available.