Im going through the book a second time with a fine-toothed brush and restudying - so stupid questions may appear.
I understand there's a Root switch elected through the first STP process with the Bridge ID (Priority and MAC address). After this process is completed and the Root Switch is selected, the Root Switch is the only switch that can create BDPUs.
With that in mind, the Root Port selection is really a broadcast storm of Hello BDPUs (from the Root Switch) that add to the "Cost to reach root" field.
Am I correct in thinking that the Root port sends the BDPUs?