How to understand it
The Moon changes signs more quickly than the Sun. The ascendant changes with time and location, so an unknown birth time should leave it unknown rather than filling in noon.
An example
Suppose someone reads a bold Sun profile and a private Moon profile. The contrast can invite a question about public and private behavior without forcing a contradiction.
Use it carefully
Check whether a birth time came from a record or a guess. The confidence of the input limits the confidence of the interpretation.
Try a reflection
Which description reflects a context you can name, and which does not fit?