Earlier quoted context omitted.
Maybe I'm too software-engineer-brained now, but to me it seems like lawmakers should just be using a tool like git directly. The legal code is a codebase, every bill is a PR, the arguments and proposed changes are captured in review comments, and the PR is accepted/rejected on a vote. Aside from "lawmakers don't/won't understand the tool", why not do it this way?
I think they pretty much do, it’s just not recorded as such in an easily retrievable format.
However, the draft stage isn't documented this way. Members negotiate whatever between themselves (well, really their staffers) and this happens over email, in discussions, via Word documents - whatever works.
I guess in the git metaphor, drafts are in flux while being worked on as a commit, and are squashed and then accessible as such squashed commits once initially introduced or whenever they lead to bill amendments. You can't necessarily track down what member was responsible for a specific sentence in an amendment.