Easy. "We are expecting the most recent available version of Visual Studio (by the time the contract is signed)".

Step one level up above the trenches and the people you meet haven't had the time (or even skills) necessary to study the details to determine the fact that "Visual Studio for Mac" is, in fact, not the latest version of Visual Studio in the slightest. And why should they. Delivering a visual studio solution should be as unambiguous as delivering an excel sheet.

That's really interesting. You're not talking about finance or engineering, but yes, it certainly seems possible that there's a business that does things that way.