The next line in the second link reads:
Do not fetch data during a transaction unless the transaction is very quick, but it's not recommended.
So you can read/fetch within a transaction, if you are sure it would be very quick, or if you want to apply read locks on these rows until the transaction ends.
But generally this is not recommended, as a good practice I always try to fetch outside of the Transaction, except in edge cases, when I want to lock these rows for reads until I finish.