Yep, that fairly well sums it up. The ideal aim with the kapton and ceramic tape is to stop heat directly transferring to the AL block itself, and as the threaded section is directly connected to the heater block some latent heat will transfer through it, so the thread is coated in the thermal paste to help draw heat away from it. I'm unsure of what the material is in the thread but from heat transfer mechanics, aluminium is a much better conductor of heat that steel (assuming stainless steel is the thread) - stainless is bad at conducting so theoretically it would hold a lot of heat, which is basically why I used the thermal paste - it essentially helps to conduct excess heat away from the threaded tube

Hope that helps!