It takes forever to repack 70+ locales with only one machine per platform. If I forget to reduce the number locally (since it has been a long time since my previous fake release and I probably won't remember to do it) I would have to either start again or face the redness on updates generation if I decide to abort some of the locales. See documentation: https://wiki.mozilla.org/Release:Release_Automation_on_Mercurial:Documentation#Doing_a_test_run_with_a_limited_number_of_locales

In my opinion, having this as the default is an anti-feature. It's certainly useful for specific testing, but when doing a real staging run of an upcoming release, we should be testing all locales. We've tried doing limited locale runs of such things in the past, and have missed problems because of it. Resolving as WONTFIX, please re-open if you disagree.