In the abstract, the word ‘Interchange’ isn’t inaccurate. I agree with you, however, in this specific case because of the use on the tube map of the words “internal interchange” which does normally imply a lack of gateline obstructions or OSIs where there are gatelines. (I can’t say that’s an absolute truth but it could be a fair interpretation.)
Of course, none of that is implied or stated in the use of the word ‘interchange’ but it would be clearer to use different terms for different circumstances on the car line diagrams just as they do on the tube map.