Except that when using nautical miles it goes against your theory.

Using statute miles, in a nautical work, to provide evidence for your theory is deceptive and you should have provided both versions rather than choosing to deceive through misrepresentation.

If the measurements presented were miles then he should have used miles. If you want to know where some distance in nautical miles falls along the trendline simply convert that distance into miles and find the x coordinate whose output is that distance in miles you are using. Converting his use of miles to nautical miles would yield the same results as the actual distance is still the same and as long as the conversion is done correctly the equivalent distance in some other unit will by definition still be the same distance. If something is 1000m away and you want it converted to kilometers, that object is still 1000m away, only now your gragh has it as 1.000km. You are literally asking him to apply one additional coefficient which graphically appears as a compression or stretch unless a different scale is used to compensate; if the latter is true the two graphs will be identical