Well it is copyright to the CAA although the topo info is also digitised to CAA specs, topo really isn't the issue. But providing all amendments have been issued (and read) by the user if you fly through a bit of sky the map shows free of all CAS "ipso facto" your clear of any infringment.
Practically, I agree with you but for people planning on skirting very close “on the map" do they know what the printing tolerances are? 1:500,000 means half a mile is less than 2mm. Also, there are two sources of data: the coordinates in the AIP and a printed map - in a conflict, my money would be on the former being the only actual “official” definition.
In reality, I don’t think you’re going to get the full weight of the law on the back of your neck for drifting marginally inside a bit of airspace but it’s probably better not to offer yourself up as a test case...