it is standard in big companies, I work for one.
Sarver was probably not even in Phoenix if they did it via "phone".
I feel like you're being argumentative for the sake of it.
Does it happen out there in the business world? Yes, it does.
Are the Suns a 'big' company? Linkedin suggests they are less than 500, and my guess is that 90% or more are in one location. So no, it is not a big company.
Just because it happens out there, doesn't make it right, and doesn't help the reputation of the organization and/or Sarver when both are low right now within the league.
If Sarver knew he was going to fire McD, and CHOSE to do it over the phone instead of in person, given the circumstances, that says a lot about him.
It's slightly more understandable if it was in the heat of the moment in an argument as Phrazbit suggests, but still isn't a great look.