So you justify the printed scale bar by the size of the doors. If I use the map I can ignore the scale bar entirely and simply say the doors are probably a meter, or 6 feet. Since we're already talking about 'heroes' not people and the difference between a meter and 5' can be entirely absorbed into the inaccuracies of the map and the game system involved I don't think its a very worthwhile argument.There is a scalebar in the first image to verify that he is drawing the grid to scale and in the others all you have to do is look at the size of the doorways to see that it to is scale.
Since I never expect to build my game maps I am pretty flexible about reinterpreting them.
I'm sure the guy is honest and making a fair argument but he could just as easily be cheating all over the place. DM's have no constraints or tolerances to obey. (That was the point behind my mentioning the various times the map was scanned)
In most RPGs, regardless of the printed scale, I'd approximate based on the inhabitants and the map use. If his temple was a hobbit temple, the doors might be only 2.5 feet wide. If the temple was for Storm Giants 15 or 18 feet wide. Same map - my squares would adapt it so I (respectfully as well ) think its pretty arbitrary.
I appreciate the meter thing (and don't disagree) but I think his mapping examples are pretty unconvincing.
I'm more convinced by the merits of a base 10 system that is easier and more modern.
Sigurd