Much of the thermal gradients would be stable and thus would not change that much. It is mainly the part of the thermal gradients that does change, that could be trouble. Sources for this is the changing heater power of the LTZ and the heater transistor and to a smaller degree the diode. Another factor it heat loss from convection, if the instrument is tilted.
Temperature differences between the critical pins (mainly pins 3 , 7 and 6) can add thermal EMF, that can add to the final TC.
The tricky part is finding a good balance between thermal gradients that would favor thin long lines and low copper resistance that would favor thick copper.
With the thermal camera reading emissivity can be a factor - especially readings on metallic surface are not real. So the small gradients close to the hot LTZ1000 might not be all real, but could include environmental radiation and also heat flow by convection if the board is tilted. It still is nice to look at the thermals.
From below the temperature around the LTZ looks really nice and even. At least one of the two slightly colder pins is the rather thick ground connection and thus not a surprise. The other could be due to the lines going there too. Things will change with additional cover anyway. The more telling thermal picture would be from below, with the cap on the top side mounted.