I think you are right "OSI approved license" is a much more precise term than "Open Source".
If OSI wanted to provide the official definition for what is "open source" and what is not, they could have perhaps trade-marked their term "Open Source".
But "OSI approved license" has its own vagueness about it. What does it mean that OSI "approves" a license? Approves it for what? To be called "Open Source"? But then unless they have the trademark for the term Open Source, they shouldn't be the one to give approvals for people to call their software that.
This reminds me of the debates about whether something is true Agile, or merely wannabe-Agile. Words are just words. It is good to have precise definitions but those can be specific to a given context. It is a bit like let x = y + z. Is that the correct definition of x? No, but it is a VALID definition of it, assuming y and z are well-defined as well.
If OSI wanted to provide the official definition for what is "open source" and what is not, they could have perhaps trade-marked their term "Open Source".
But "OSI approved license" has its own vagueness about it. What does it mean that OSI "approves" a license? Approves it for what? To be called "Open Source"? But then unless they have the trademark for the term Open Source, they shouldn't be the one to give approvals for people to call their software that.
This reminds me of the debates about whether something is true Agile, or merely wannabe-Agile. Words are just words. It is good to have precise definitions but those can be specific to a given context. It is a bit like let x = y + z. Is that the correct definition of x? No, but it is a VALID definition of it, assuming y and z are well-defined as well.