That first picture is from after I busted all the baked stuff loose from the funnel fingers. Small pieces of baked tar on top of the wood is what you see. I picked out only the big ones not to let too much tar down there to burn at once.
But, you’re right. My upper nozzles are not even an inch from the firetube top and I might run a little hotter in the funnel area. Still the chunks don’t get toasted that early, but they sweat. Mixed with debrie their sweat bakes some over time whenever you run the wood down low.
My temp probe sits at the top of the hopper. 70C is normal temp. At 80C I have about 10 min until the alarm goes off at 100C. That’s when the probe is getting exposed to radiation from the glowing char and fuel level is only an inch or two above nozzles.