Attention, I was using it with a relative path and it worked, the behavior change is that it stopped working, I believe with one of the two updates below:
September 4 fetchmail (6.4.0~rc4-1) unstable; urgency=medium * New major upstream RC release. * Remove outdated and Python 2 only fetchmailconf package (closes: #936512). * Drop merged in patches. * Update remaining patches. * Remove old upgrade code from postinst. September 6 fetchmail (6.4.0~rc4-2) unstable; urgency=medium * Remove all parts of fetchmailconf (closes: #939522).