Depends how the inlet and outlet align, and how fast the water is moving. The upper hose comes into the top of the tank - water could be rushing to the bottom of the tank and going straight across the bottom toward the outlet (to the pump). No idea if the end tanks are baffled, or have any other design features to prevent this kind of flow establishing itself - but it's definitely possible.
I'd be checking all over the core and seeing if you can 'map' the heat - or even get/borrow a thermal camera to see if there's anything to see.
Also, a hole in the thermostat won't bleed all air in all circumstances. That upper 'loop' in the rad hose could be trapping air in the system if it's the high point in the routing. Even without something like that, I often have to massage the rad hoses while filling to force as much air out as I can.
