Well he said he’s just adding these little pieces to help support the new concrete and keep it attached to the old concrete
Now could stray voltage hit those rebar dowels and not my copper wire since they aren’t connected?
Stray voltage does not "hit" something. It is not as if stray voltage is zipping around looking for a nice chuck of steel to manifest itself it.
Sometimes it helps to think of electricity as water. This is going to be a little general not quite technically factual, but it will help (I hope)
Think of electrons like water. Water wants to find its' own level. So do electrons. If I have water in my pool and it is higher than my pump, if I open my pump skimmer lid the water is going to start running through my pipes and come out the lid.
Electrons are the same way. If I have a large collection of electrons somewhere and a small connection elsewhere, and I connect the two with a pipe, the electrons are going to run through the pipe. For electrons, the pipes are conductors - your bond wire. That is why you bond the pool water, the metal on the equipment, the metal around the pool (stairs, lights, etc) the pool itself (rebar or pool walls for ABG) and the rebar grid in your slab. You are connecting all of that stuff with an electric "pipe" so that the electron density in all of those things evens out. If you do not do that, and more electrons collect in one place than in an other and you touch both, then you become the pipe - and that hurts.
So for your rebar pins, I would not worry about it. Normal rebar in a slab is all tied together, it is one large bonded system. Concrete itself is conductive (more than the earth it is on at times - look up a Ufer ground). The worry with a large rebar mat is that it is a large highly conductive mesh, that at times can become exposed. Your dowels should not be an issue at all. I myself would not worry about bonding those.