I think most of us use more than just two adaptations of our basic speech.
The way i converse with my coleagues is different from the way I talk to my wife, which is different from the way I talk to my children ... and so on.
I think the point is valid/
I have pointed out to all my girls as they have gone through to maturity that one of the hallmarks of a mature individual is the ability to tailor your speech patterns to your company - which can help in some situations - example -
a colleague of mine, now retired, was in the merchant navy during the war, escorting Russion convoys. As you can immagine, in those circumstances, language between sailors could be a little 'salty' at times.
When he came to visit his girlfriend's (now wife, so obviously the parents let this go!) parents for Sunday lunch for the first time, he was understandably nervious.
So much so, that in a moment of panic, he forgot where he was, and enquired of his potential mother-in-law if she could "Pass the fu*k*ng butter ..."
Like I say - matching language to surroundings is a big help in getting on in life!