Rusty A300 - yes, you are right. You MUST maintain V2+10 till 4000' before beginning the acceleration.
I think you're right also that "climb to XXX before level acc." is only used for terrain considerations, though it may also be airspace-related in some places (ie to keep you out of a conflicting SID/STAR) - I don't think it has anything to do with noise abatement.
Unfortunately I haven't been to Athens for ages and can't remember this particular SID, but I would certainly maintain V2+10 until 4000' if departing to the north - from what I remember there are some high hills in that direction!