How does a write has a newer timestamp than a read in the transaction?

In the Design Doc, there is:

Side note: if a SI transaction reader finds an intent with a newer timestamp which the reader’s own transaction has written, the reader always returns that intent’s value.

If the intent is written by a write belonging to the same transaction Txn. Then the reader from Txn should have the same timestamp as the intent. How does the intent has a newer timestamp?

You’re right, it shouldn’t be possible for a transaction to write at a different timestamp. I think that part of the design doc is simply outdated and predates the discoveries that are documented here