I would also agree that the common sense definition of open source should be public/accessible code. But FOSS is a well-established movement and anyone involved with software development should be well-acquainted with Free vs Open.
Almost every word has some special meaning depending on the context it's used in. This is not controvercial. This is a silly argument to try to make a thing out of.
Jargon terms are necessary for specialists, it's true. Berry, for instance, technically includes tomatoes and cucumbers, but not strawberries or raspberries. So if somebody says "I just bought some berries" you should inspect their purchases and correct them accordingly, because maintaining correctness is important.
