If you already know RoR and have your dev machine and deployment environment all set up, then it's not hard to get a Rails app working. Rails has a significant advantage with the use of gems (and bundler, etc.) for easily adding complex features.
I still use PHP for my home projects most of the time because I haven't bothered to set up Rails on my VPS, so the effort it would take to do so just isn't worth it compared to how easily I can drop a PHP app in place. (I am using a framework in PHP too.)
But then, the author was talking about PaaS not setting up Ruby on a VPS. So in that case it's probably just about how comfortable the developer is with each language. I'm a bit more comfortable with PHP because I don't like debugging Ruby GEMs that use instance_eval black magic for DSLs and/or have to be inserted as Rack middleware. Not unless the project is large enough to make Ruby gems worth it.
(Eg. if I want good unit and integration testing. For home projects I rarely do integration testing. E.g. #2 was rack middle ware for REST API.)