A "cycling computer" for me is a system includes both a recorder of cycling data and a display that's always visible while cycling. That can be a single unit mounted on the handlebars or a head unit on the handlebars with the computer and recorder, in say, your back pocket.

Having just a smart phone in the back pocket recording data is a fundamentally different use case than having a computer display on the handlebars. Looking at a map or course or power or speed or cadence or heart rate data after the ride is not the same as having it displayed live.

Comparing smartphones to cycling-specific computers has to include either a case and handlebar mount, plus any battery extenders that might be needed for long rides, or it has to include a separate display like the RFLKT.

Of course, if you want just a recorder for your home or online cycling log, then using just the smartphone in the back pocket becomes more attractive.