Not to be pedantic, but that's not necessarily true; we've had 1 major chain split before that killed ##'s of blocks containing thousands of transactions.
And also transactions that don't make it into a block will just die if the original node doesn't rebroadcast it. So after 1 confirm it's mostly irreversible.
To be truely pedantic, at the time they were on the Bitcoin blockchain, it wasn't until well after the incident started that the developers and pool owners decided to reject that blockchain (which was just as compliant with the stated Bitcoin rules and had a mining majority) and switch to the other side of the form.
To be pedantic, those aren't really 'reversed transactions' so much as 'data loss'. It's not like specific transactions were targeted. If a bank incorrectly recorded a credit card purchase of yours, you wouldn't classify it as 'a reversed transaction'.
If the goods you purchased are already in your hands, and your bitcoin payment has been lost in a blockchain accident, what is your incentive to rebroadcast your bitcoin payment?
And also transactions that don't make it into a block will just die if the original node doesn't rebroadcast it. So after 1 confirm it's mostly irreversible.