RAH - Here is what I think caused some holes in the ice cover with unfrozen water away from the pond edges.
My pond also had 7"-8" of snow cover on mainly 4" of ice. When I went out to collect my water sample by drilling a 6" hole in the ice, the weight of all the surrounding snow on the ice caused a lot of weight on top of the ice. All this snow on only 4" of ice put downward pressure on the iced snow area around the newly cut hole and water started noticably upwelling through the hole onto the ice until the down pressure was not strong enough to force anymore water onto the ice. After a short time while collecting the water sample, I was standing and slipping in at least 3/4" of water with water still upwelling out of the hole. The next morning I estimate at least a 50ft diameter of underlying snow of about 1" thick was water logged and then later refroze in the 0F-5F nightly temps. The next day there was still some unaffected clean snow topping the frozen snow layer below. I have seen this type of thing years previously. However in those years the nightly temps were not cold enough and the next day a slushy layer of wet snow remained under a thin layer of frozen ice.

With enough snow weight on 4" or less of ice this down pressure from snow weight I think will evenutally cause water to start seeping up through a crack or thin spot in the ice. As the water finds its way to the top of the ice, the moving water gradually melts some ice and enlarges the ice hole to allow more water to upwell through the ice hole or widen the crack. This keeps occuring until the down pressure of the weight of the snow equalizes to the strength of the ice thickness. When a pond freezes, I find that the increasing thickness of ice surface layer is not perfectly level and some pond iced areas are a little higher than other areas probably due to the expansion of the ice will heave or force some areas of the pond surface upward.