This does not seem to be the case in my document. I can do Select -> Select All -> F9, do the update, over and over, without making any (other) updates to the document in between.

Then, once I do "Accept All Changes in Document", the Update TOC dialog box does not appear. The same non-appearance continues if I delete headings. The TOC does not get updated, and the deleted headings still appear in the TOC.