FWIW, my Centos 7 install doesn't have ftp installed and yum has no apparent issues.
I also, mainly, use Fedora (22 currently) and it hasn't had ftp installed for a long time. Of course it uses dnf now, not yum.
If I understand you correctly, if I uninstall the ftp client, yum will not use it as it cannot. Is this the case? I had assumed that the code underlying yum had its own stack for dealing with ftp://... urls.
I will try this on a couple of machines.
Thank you, Bob