Good day Jose, I'm not sure what you are asking... You can create as many companies as your computer can hold in your Sage 50 application.

When it is reported that sage 50 pro does not allow multiple companies, is it only referring to the ability to keep more than one company open at a time?

No, I don't believe that is correct either... Where are you getting this reported information? You should be able to open more than one company at a time as noted in this article: How do I open multiple companies at the same time? (sage.com)

You can only open multiple companies at the same time with the Premium and Quantum versions.

Yes, it is.  You can create as many companies as you like, but you cannot OPEN them up at the same time with Pro.  With Premium and Quantum, you can open 13 companies at the same time! 

I understand the title but that article does not even refer to this question.   I think they need a do over!  LOL

Usually the articles do a good job of saying when certain flavors isn't allowed to do certain things, I didn't see "Pro" being excluded in the article so I assumed that Pro can open more than one company... That is why I shared the article.