Installed new radiator, thermostat, hoses; engine running hot, lower hose cool

I installed a new Denso radiator in my 2012 Honda Civic LX. While I was in there, I replaced the thermostat (AISIN) and hoses (Gates).

Everything seemed to go fine. Used a coolant funnel and bled the system. Fans confirmed working when I turned on the AC. Heater works fine.

Honda decided temperature gauges are dumb, so I'm actually using the heater temp as a proxy and this shit got hot. Hot engine light never came on but I pulled over let it cool for a bit then finished up the short half mile home.

When I opened the hood to let it cool, I notice the top hose was hot but the lower hose was cool to the touch. I had tested the thermostat in hot water at the recommendation of another redditor, so I'm assuming that's not it. I spent like half an hour bleeding the system so I don't think there's air in there. I didn't flush the system so I don't think I knocked any debris loose to cause a blockage. There are no signs of any leaks at all. Hoses aren't bulging.

Any thoughts? The radiator didn't come with any caps, so it it possible where the lower hose attaches has an internal plug or some shit?