Hi hotmetal.
'Not trusted' is a harsh way of putting it.... (But probably true
) there could be many many many reasons why you are being given this.
a) For years I have had drummed into me that aircraft can't go down and slow down. Therefore if I need the height restriction then I will say this as the level is more important.
The level by restriction could be for many reasons... it might be there to separate you from another aeroplane, or someone else's airspace, in which case I need to be sure you will make that level.
b) Maybe I need you to not slow down initially so you keep your place in the queue?
c) Maybe I've got another aircraft coming behind you who is not yet level separated but will be once I've got you level, and if you slow up that could erode my separation.
These are just a couple that spring readily to mind...
If I can let you slow up early I will, and regularly do. We just have to try to balance everything for every flight that we work, and sometimes that means you don't get exactly what you want. (don't mean that to sound harsh...)
Keep asking questions and see if you can come to visit us sometime... we all need to learn so much more about each others profession. (I readily admit that I should know more about your job than I do...)
Cheers,
Northerner
"Keep smiling, it makes people wonder what you're up to... ;¬)"