@apri I figured out how it works (in terms of why I had mons that were HTWT 0). But you’re probably out of luck.
if you want to keep a Bank transfer Pokémon to have HT/WT 0 (resulting in scale 0) in HOME v3.0.0 (and other stuff, such as old HOME events), it needs to have entered PLA before v3.0.0.
Once it gains a scale, that value sticks, and the HT/WT doesn’t get rerolled. As of now the rerolling is random, as I’ve got clones that gets different values, meaning it’s likely not derived from some other value on the Mon.
edit:
If you're looking at the chance to generate a mini/jumbo via HOME, read the Tweet thread