I wouldn't call it a splice either, but I think there may be some other issues. If each (or just one) wire from the panel to the pipe is sized per 250.66, then I see no problem. However, if these are GEC taps and a full size GEC was not run to the pipe, then I don't know if that meets the requirements of 250.64(D).
I see that the first 5' of a pipe can be an electrode, and used to bond other electrodes, but can that pipe be the full sized GEC itself and small taps from from it to panels?
Personally, I don't see why it can't be done this way, but I'm not sure this is permissible based on the definition of GEC. But running a short stub of #2 or 1/0 from that pipe and split bolting taps to it seems like a worse implementation.