Earlier quoted context omitted.
(In this subthread it is just github because we were discussing enabling parallelism for github only. The terminal proposal meant "keep it single thread for CI")
Okay. The problem is still present in the GH case, although to a lesser extent. These kinds of complications on a "same experience for everyone" flow are also nontrivial: single-threading on CI is hard to explain to users who see very fast local installs and slow CI installs - the latter costs them extra money! - and complicates the story with mirrors, download groups that include non-GH origins, etc. That's not to s…
I suspect they are wrong in this specific care based on the "every other package manager solved this" heuristic, but I have no doubt this is not a straightforward issue.
Personally, I dropped the case after offering to send a PR and getting back a "we won't accept this, it's not because we didn't think of it, from where we're standing it's a bad idea". They may or may not be wrong, but X am definitely wrong here, knowing almost nothing about it.