Brass skimmer covers are metal and brass is a great conductor. So yes they have to be connected to the bonding grid. If you didn't take this into account when you constructed the deck there is a problem.
Some possible solutions (though maybe not for you) are that IF you water is bonded by a waterbug in the skimmer then you just attach to that. That is only a half solution to the problem if you have two skimmers. depending on how much work you want to go to and how yor deck is set up, drill under the deck and fish a wire through. This is heca amount of work and can be very frustrating.
As to its only 1 or 2 volts. Yea that is generally correct if we are talking about normal stray voltage. The problem with that is that who feels and is effected the most by low voltage? Children. The smaller the better. They are great low voltage detectors. So if you want your three year old yelping when they step on the brass skimmer cover on a wet deck- this will do it.
But what if its not just 1 or 2 volts? Watch this video:
Surveillance Video Shows Children Shocked in Swimming Pool - YouTube
Ok so the TV guys do not know what they are talking about. But note its the kid who is most affected, she could not break off from the current. I'm not even sure the adult felt anything.
So greater voltages are possible and bonding will protect against them by ensuring that all conductive surfaces around the pool have the same electrical potential.