Nah, the reason is to split the head of the chain for a period of time, and do different things in each chain. Then when one of the heads is declared "true", you gain advantage (typically you spend the same coins twice, once in each head).

You say "nah", but what you are describing is reversing a transaction, I don't see how that is disagreement.

From the POV of the recipient, when the split branch becomes the "non-true" branch, it looks like they got the money but then it disappeared.

If you are considering the recipient a human interpreting the results, then this is a failure of their wallet UI. The block chain is a tree not a log. The views that show it as a log are just showing you the statistically most likely outcome. If you look at the raw data you see all possibilities.