The patterns for straight sizes ( 0-18 ) scale accordingly because the people wearing them still resemble humans.
Once you're outside of that, the bodies are going to vary due to fat distribution (Anna's candy juicy thighs, Jaimie's massive apron pannus, Tess's gargantuan upper arms, etc.). You can't take one pattern and make it fit all of the fatties the same. This is why most deathfat fashion = stretchy tarp.
Wear the sweatshop tarp and collect your disability checks, fatty.
You can explain to these deathfat "activists" over and over again that larger plus-sized women (anything over a 3X, and even the 3X is dodgy) are not a profitable group to cater to, and that this is why the options from a 3X on up are basically stretchy tarps. You can talk yourself blue in the face, trying to explain the practical realities of making those sizes fit as many varied types of corpulent body shapes as possible, and thus why stretchy tarps are the norm, and it's going to fall on (willfully) deaf ears.
These people will only listen to what they want to hear, and either ignore the truth, or claim it's a lie (without having any good arguments as to why it's a lie). Like spoiled children filled with envy of what the other kids have, they want what they want, and they don't want to hear about why they can't have it—their sense of entitlement runs that deep.
They don't know how clothes get designed and manufactured; they know nothing about the business and financial end of the garment industry, and they don't care to know, because knowing will still not get them the clothes they want. And they're all hooked on being seen as a marginalized, oppressed group because it absolves them of all responsibility for the state of their bodies, chalks up their social difficulties to "fatphobia" (instead of causes they have control over), and lets them occupy the moral high ground (at least in their own minds) because they are oppressed and marginalized.
Being fat and declaring that access to boundless choices of fashionable clothing is a human rights issue is patently absurd, but it's all they've got (okay, along with disability and gendershit) if they want to hustle up a spot on the oppression stack. And enough people have been stupid, and terrified of being branded some form of -phobic, to humor them. But since deathfats are so obviously self-made victims, and their arguments are so ridiculous, they've been the last group to gain a few meager, grudging oppression points, and thus are the first group to start losing them now that the social tides are shifting. But they'll keep on banging the drum for that victim narrative, because at this point it's all they know how to do.