It seems to be the case:

> Signal advises you whenever a safety number has changed. This allows users to check the privacy of their communication with a contact and helps protect against any attempted man-in-the-middle attacks.

> The most common scenarios where a safety number advisory is displayed are when a contact switches to a new phone or re-installs Signal, but these actions don't always result in a safety number change. However, if a safety number changes frequently or unexpectedly it may be a sign that something is wrong.

https://support.signal.org/hc/en-us/articles/360007060632-Wh...