God that's annoying as hell. Apparently the Systemd dev who added this functionality intended it for a different use case than mine or yours. They revised their implementation to better serve their original purpose without realizing it broke our (mis)use of their feature.
For convenience for anyone running a sufficiently bleeding edge distro to have this very latest release already, here's a direct link to a comment with a configuration workaround which restores the old behavior: https://github.com/systemd/systemd/issues/25269#issuecomment...
And here's the PR for the formal fix, which combines the old behavior (new config value name, read carefully) with that new 5% emergency fallback behavior, for folks who want to patch it themselves:
https://github.com/systemd/systemd/pull/25374
It's not merged yet but maintainers have approved it for merging with a few comments on config value names, so it should be safe to add as a patch.