The dealers probably don't see the issues due to the vehicles they see are well maintained.
In the last 12 months I've done 2x 07-08 320d in as many months and a 330d not long after. Becoming quite used to them now, lol.

They can apparently be done in situ on the 320, but I prefer to remove the engine for ease of rebuild. Both I've done had new upper/lower chains tensioners and guides, rockers, hydraulic followers, oil pump, oil spray pegs (in timing chest). Pretty easy job once the engines out tbh. Head didn't need to come off either of them. (PS, parts were in the region of £1200 iirc) )

All of them were down to poor oil quality, due to lack of servicing!! The 330d required a complete engine as the damage was terminal when the chain went.