Probe how Safari paints the software-keyboard return key, and whether the label can flip live when a Dash-style “submit position” becomes true (caret at end + trailing newline).
Mobile content rule: Enter inserts a newline unless the caret is collapsed at the end and the previous character is a newline — then Enter submits (logged, not posted). Empty field: Enter does nothing.
Focus each field and compare the painted return key. Labels are fixed.