that is a weird sequence. I have always thought the traditional DT/HT; ST/BB; TT/HT; DT/BB; TT/ST sequence made the most sense if you aren't using a jig. I think the reason he tacks the DT/HT first is because that joint most often requires the most blacksmithing.

Using bronze results in more BB shell distortion, that's why he heats the bottom. For many years I was afraid to try using LFB for lugs, but I finally got over that and figured out how to do it. As usual, the secret was a bigger torch (OK, enough heat, but in this case it required me to get bigger tips for my torch). I am not sure if I will ever use this knowledge for anything other than seat tube reinforcements though.