alt Hacker NewsGuilds often very much did assert what people could and could not build - historically.
Against their will.
Historically that is a major reason why guilds existed, actually.
It’s an extremely modern invention that corps have these type of power over their customers.
You've lost the thread.
Here's your original claim: "no guild ever let a vendor pick and choose what their capabilities were"
A carpenter's guild can prevent other people from doing carpentry. That is not what's being discussed here.
A carpenter's guild cannot force a horseshoe maker to begin making hammers. That is what's being discussed.
Your initial claim was analogous to "never before has a horseshoe maker been able to decline making hammers when the carpenter's guild needed hammers"
Obviously they have and any other state of affairs would be flatly insane.