Is there any rule that requires the announcer, head referee, or other staff needs to announce why the repost happened and explain it.
For example: after a match and score is ‘100 to 102’, when a score repost has changed the score to ‘105 to 102’ because of a foul, does someone need to explain why that foul occured (G205?, G201?, or other rule violation).
The manual and current FRC QnA does not talk about this
The manual does touch on something related to this topic, actually. Section 11.2.1 says “While FMS tracks quantities of FOULS, FIRST instructs REFEREES to not self-track details about FOULS and TECH FOULS; as a result, we don’t expect REFEREES to recall details about what FOULS and TECH FOULS were made, when they occurred, and against whom.” The logical conclusion of this statement is that there is no requirement to announce what the specific call was that caused the score to need fixing, because the referees are not to track those details. Obviously in practice, if the score is being fixed and reposted the refs will likely know the specific cause and time violation, and will sometimes announce part of that information, but they are not required to.
A possible scenario for this is that 2 referees called the same foul, but both thought the other was going to enter it into the tablet and neither did. (Not that that is a good thing; the refs should have communicated better, but mistakes happen.) When the score was announced, the refs realized the foul was missed and the head ref had the score corrected.
Scorekeeper here: No hard rule, but generally if a score edit changed the outcome of a match (W/L), scores get reposted. Change in bonus rank points, sometimes. No change to either, usually not (although I think I might have been asked to once in a prior year because the change resulted in a new high score for the event?).
Score edits happen due to requests from the head ref or the FTA… can be caused by referee error (or a change in HR opinion on a foul), scorekeeper error (whoops!), or FMS error (not so much this year, thankfully).