Well, it's fiddly and I have to remember to revert it back after I'm done installing - so it's several tasks instead of one. If I was doing this manually I'd just use the command line argument - it's convenient, and does exactly what I want for the exact duration I want (this one invocation). This also strikes me as a pretty common scenario, it's not like installing in-house generated, unsigned RPMs is unheard of in software development circles. :)
I could use the command module with RPM directly too, but instead of coming up with creative workarounds I'd just like to have my playbooks be as high-level as possible and use all the idempotent Ansible goodness I can.