If it creates a monopoly then no, it's not okay, no matter how normal.
It's hard to even consistently distinguish a monopoly - is it market share? Earning power? Barriers to entry?
"I know it when I see it," as it is difficult at best to rely on distinctive actions or indicators considering the fluidity of business dynamics and the market landscape.
It would change the shape, but not the definition.
So are a lot of laws and regulations. Doesn't make them any less valid.
That would be the difference of an anti-competition monopoly vs just a monopoly.