Sort of is and sort of isn't to be honest.
Its more of who is actually responsible for the aircraft and if that person makes a decision not to join into a service or leave one is it there right to do so or not.
If its legislated as it is in some European countries there are rules in place about the responsibilities of the PIC dealing with said plan and when it should be shut down and who they should contact etc.
In the UK currently we don't have such rules. I don't see it as a controllers job to make rules up even if its for the benefit of the pilots concerned. Or force pilots into what are seen as best practises for ATS to work to without it being legislated that its the way it should be done.
The poo really does hit the fan if they do start looking for the aircraft and discover the pilot is already knocking a pint back. I am not surprised that in some parts of the country they are rarely used. And I can understand why the pilot wants to make sure the plan is closed.
For me there was never much point because I never knew which route south I would take or for that matter if I was IFR or not until I got to see the wx on route. I could go down the A9, straight across the top of the cairngorms or round to the east or round the coast. Or IFR over the top.
I just used to tell Scottish info what I was doing when I had decided.