The install script and the whole tarball distribution was designed without uninstall support in mind and it's very bad for doing so. Software that do not offer uninstall script should be considered as malware.
It offers the option of separate prefixes at startup. I usually use that, and simply remove the whole prefix, rather than mixing system managed and private binaries. That never has been a good practice. Uninstaller script or not.
The FreeBASIC project, despite being smaller they designed a simple but worked install script. The most important thing is I could uninstall it simply by issuing ./install.sh -u.
It would be nice to have and also interesting how they do it. I think the problem is that the install.sh simply extracts a bunch of .tar.gz based on query results, and there is no over arching filelist.
The script is also so old that I don't even know when it first was introduced.
But the manual removal should take no more than one or two minutes. Is this really worth all the drama?