Truckflyer:
Maybe I don't write a good English.
So I explain again my point for you:
If ATC tells me 1024 OF COURSE I set 1024.
BUT I might make a mistake and set 1023 instead of 1024. This could happen to you as well.
Then I (and you should too) check my altitude indication and compare with apron elevation.
If the difference is too large, I must question either the QNH setting, and then ask ATC again for the QNH, or question the serviceability of my altimeter if after having checked again with the ATC the error is still too large.
But if the error is within acceptable limits, I will have NO REASON to question my QNH setting.
The next opportunity I will have to check my altimeter setting will be my first check after take off, and then, if I wrote 1024 on first contact, I will correct it. If I wrote 1023, I wont.
So it will only be when the next ATC tells me a QNH, after changing from TWR to the information service, that I will have another opportunity to set the correct QNH.
I think that, in a VFR flight, there is no real safety issue in that case, and that a CPL applicant should not be failed.
You should not expect a pilot never to make mistakes, you should expect a pilot to have a method of work that will permit him to keep his mistakes within acceptable limits, and to correct them at the earliest opportunity.