I have come across a lot of people claiming they know how to judge what professional software is. They were wrong many times
I see professional software as something making money.
Gtk logs errors and spits them out into stderr and (if needed) elsewhere. Qt does a similar thing, you can alter the behavior using environment variables.
The notion of having something that is tested and "perfect enough" that there will be no issues is just naive and will never work. Software is complex, it is always broken. You always want to know what breaks in which circumstances and fix that. You want as much info as you can get when an error happens.
PS: I don't deal with much "RTM" software. Most of my work is open source, my platform of choice is GNU/Linux. The only RTM software I work on is Fedora for their release CDs. These definitely have issues and all sorts of things are logged including what you might call GUI operations.