Understanding SC 4.1.3

Please can someone help me   understand the basis for the assertion in
the Understanding doc for SC 4.1.3:
"This Success Criterion was intentionally worded to apply primarily
when visible text is added to (or becomes visible on) the page"
I do not see where the normative SC text / definition of the term,
"status message" suggests this.

Further, the Understanding doc seems to exclude from the phrase,
"change in content":
- Modification of status text;
- Non-textual status content, such as images.

If a waiting state  / progress is indicated via a non text method (an
image), that is not a status message?

Or am I not understanding this correctly?

Reference: https://www.w3.org/WAI/WCAG21/Understanding/status-messages.html

Thanks,

-- 
Sailesh Panchang
Principal Accessibility Consultant
Deque Systems Inc
Phone 703-225-0380 ext 105
Mobile: 571-344-1765