The way I read the post. Which is maybe me reading in what actually happens sometimes.
When the frq is near saturation and the controller is going like steam train hardly pausing between read backs and the next instruction.
When you get transfered onto freq you can't get a word in without stepping on someone. Or when you do think you can get in all you hear is "stepped on break break...." Then out the blue you will get an instruction eg "xxx climb flight level 160, turn heading 350 degrees". You read it back and off you go. I presume what the post was meaning was that if you do get an instruction before booking in so be it, service as normal from then on. Whats not being checked is the Flight level your at/passing or the clearance you have been given by the previous sector.
I am quite sure the controller was less than happy about having to work like that. It opens up a can of worms if anything goes wrong. You are aready working with 5-6 dominoes in a line for your accident domino race. Its not pleasant for either party.
I seem to remember a few Chirp reports recently on this subject as well.
MJ