I guess it is just a human thing, INJS, either hearing but not absorbing, 'habits' - assuming 'old' procedures are still the norm, etc. Believe me, we do TRY to get it right. It has recently arrived on the Stansted ATIS as well.
Out of interest, is EOBT adjusted for slot delay in your system or does it remain based on original planned departure? The reason I ask is that in order to call 'fully ready' for a delayed slot we need to talk to you somehow to find out the latest slot and a clearance. Most airline SOPs do not allow 'fully ready' without an ATC clearance, thereby enabling instrument/navaid setup and crew briefing. I now that abroad it moves with slot at some airfields. One cannot rely on dispatch keeping you up-to-date on slot movements.