Actually - it isn't. AERAD make no comment of this at all
I'll check out the AIP at work on Monday, had all departure charts of EDDL in my hand just last week though and they had it printed on them.
Perhaps that differs between charts from different sources (Jeppesen, DFS)?
Again, not my experience. Departing from Tempelhof about 2 months ago. No mention of change automatically on the chart, however, we expected it (being Germany) and did so. Departure frequency on the chart was different to the frequency we were actually required to go to - no mention in the clearance, no mention on the ATIS.
Such practice is fail dangerous, and as such is in need of review.
Such practice is IMHO not that dangerous if all parties concerned act correctly - which includes the printing on charts and the pointing out via ATIS/clearance if the procedure changes.
Mind you, I am certainly not a seasoned ATCO, merely judging from what I have seen and worked with here during the last few months.
So feel free to take what I am saying with a grain of salt.
Regards,
Robert