Be careful about your interpretation here. My own sensei spent 10 years learning aikido in Japan, and when he's on the mat a bunch of Japanese mannerisms and syntax reappear. But it's not put on--that's the context in which he learned aikido, so being on the mat re-creates them. Might be the same for the guy you saw.
Also, there's value in ritual itself, if the activity you're engaged in has any significance at all. We create ritual to express the significance of what we do--even a baseball game has ritual, as the roshi of the Zen monastery I visit used to explain.
Valid point - it's all a question of degree, and perhaps a matter of personal preference and style. You pays yer money and makes yer choice!
Done in a genuine way, I have no problem with it.
The ritual of the dojo ties us to the history of aikido and has value in itself--if we don't use the ritual that's given to us, what do we do instead? Invent it?
I don't think we should be frightened of inventing our own rituals - though of course there are plenty of dangers inherent in this.
Each dojo in any case tends to have its own personality and way of practice. As a teacher it is obvious to me how my own bad habits are magnified in my students!
The core for me is respect and a spirit of research. For example my major influence has been Inaba sensei of the Meiji Jingu Shiseikan - he frequently talks about and demonstrates how his own Shinto beliefs are the core of his Budo. But he also says that he is not seeking to convert people, he is instead challenging them to find their own core consistent with their culture and heritage. There are times when I "channel my inner Inaba sensei" on the mat - I am sure that can look strange to others too.