Normally I'd agree with you, but I can pick my swim lesson time and I don't have to worry about headway timing because I know when to leave and the train is timed. For untimed services, certainly I'd believe it.
These are complaints of generality that don't have relevance in the specific case.
- the time between now and the journey start time
- delays
So you would need to budget an hour each way, i.e. a total of 2.5 hours for a 30 minute swim lesson.
Imagine doing that for every single thing you need to do.