I'm not claiming that there's a bottleneck in kernel commits. (I'd guess human code reviews checking quality is the ultimate bottleneck.)

I'm saying that using emails as "building blocks to reconstruct an pseudo ALM" instead of using an actual special-purpose ALM -- is the only realistic workflow that would be accepted by the disparate Linux community who don't work for a single employer. (If you're a single company employing all 4000 of Linux kernel programmers, you could impose an ALM tool be mandatory for code reviews, assigning work, tagging bug reports, etc.)

Discussing positive bullet points of email ... even though each bullet point is true actually obscures the underlying reason the devs won't use an ALM.

I guess I don't understand your question. In Linux, the email-as-the-workflow[1] has been agreed upon from Linux Torvald and his lieutenants all the way down.

I suppose that if a one refused to use email-based-workflow, they'd have to find a Linux kernel maintainer to be a champion for their proposed changes and submit them on their behalf. (Is this a common scenario? I don't know.)

If a rebel Linux kernel programmer insisted on staging changes for review in Gerritt/JIRA/github/etc, he's going to be isolated in an island because he's not part of the agreed-upon workflow: emails.

[1] https://github.com/torvalds/linux/blob/master/Documentation/...