Hi! Maintainer here.

In short: maiao supported stacked PRs on GH, before it existed as a feature :) Now that it's exists (beta), it simply does "progressive enhancement" and adds the PRs to the native stack. But you could still perfectly function without it. That's how maiao works on Codeberg, and Bitbucket, for instance.

GiLab has an interesting approach where they auto-stack up until 20 Merge Requests, if they're chained.