baseRelDIr is not settable by end users of netlify causing new forks of a site created prior to 2019 to never be compatible with netlify.toml in the base directory.
No updates and I don’t believe there would be. What we can do is, you can migrate your site to the new behaviour (paths relative to base directory) and we can flip the flag on your site so it uses the new behaviour. That way all the new forks will stop running into the issue.