In 2019 there was a talk about data mining the DB arrival data [1] (yes, this problem is nothing new). One of the takeaways was that on some connections you can actually buy a "Sparticket" (cheaper, but only valid for a specific train), but get it upgraded to a "Flexticket" (more expensive, can take any train on the route) for free. This works because a delay of more than X minutes removes the specific train requirement and some routes are nearly always delayed by at least that threshold.

[1] https://media.ccc.de/v/36c3-10652-bahnmining_-_punktlichkeit... (German)