That won’t help. The logic to retrieve a bunch of gems is entirely within Rubygems. We ask, “hey can you install a bunch of gems for me?” by running bundle install, which calls off to something inside Rubygems. That then makes a whole pile of requests, too quickly, and gets a 429, which is doesn’t politely handle. We could retry that, but hammering away repeatedly at a service that’s already said “you’re going too fast” doesn’t seem like the way to win friends and influence people.
Short of reimplementing rubygems/bundler inside the Discourse update script, there’s nothing that can be done outside of rubygems to fix this problem.
Also, why did you create a new topic for this, rather than continue on the existing topic?