In reality nobody will have actually broken the rivets to access the ECU, I was using it as an example of the lengths VW went to.
The car would have either been mapped via the OBD11 port or had a tuning box added (and then removed before sale in the latter’s case).
There would be no way of knowing if it had an OBD tune unless you got it on the dyno and even that could theoretically have been easily removed.
The only tuning box I’m aware of that fits using the actual ECU loom (and therefore the cage needs removing) is from Abt and that’s “factory” warranted in Germany anyway, plus it costs an arm and both legs so almost nobody ever bought one when you can get a Racechip or DTUK for much less and they’re much easier to fit and remove.