Well I only saw the hose at the bottom of the reservoir when I tried to remove the reservoir to clean it out (so I didn't). But the hose goes toward the fire wall so it will connect somewhere with the engine but where I didn't trace it. Might be via a heater connection, don't know but it does eventually connect back with the radiator, as when I was draining the radiator, the reservoir was draining also (albeit very slowly).
The top of the rad does get covered but may take a few heatup/cooldown cycles to get the air out. I found this out when replacing my radiator. Better check the caps on the rad and the reservoir as the rad shouldn't get air in it with adequate coolant in the reservoir.