the insurers are assessing the risk not the just the type of items they are insuring. They look at total value of the risk you are proposing not the fact that one item is worth £350 AND ANOTHER £5. That is the job of the assessor in the event of a claim. As long as you are honest and document your items then a claim should be honoured in theory. Mine have not asked me to list individual items they are only interested if a single item is over a specific amount.
In the end the individual has to insure with who they feel best may meet their claim. Specialist insurance will give you that peace of mind but I bet you the underwriter of the policy may well be the same one as the contents insurer uses !
I doubt a burglar will take my arty cap over the lap top, providing of course they get past the two police dogs that live in the house and the intricate defence system surrounding my jager cap......