IRL, you get people who miss their measurement unit (cm or inches seem to be complicated). Or they misunderstand instructions and thus just enter 10 cm while they should enter 10.5 cm.
However, there are online stores for custom made shirts (with lots of measurements) and it sometimes works, depending on the dedication on the user's side.
Also, try doing the first few shirts individually (typically there are discounts for buying 4-5 at a time). You may need to have 1-2 great-but-not-perfect shirts first. But once you nail the measurement, it's easy from there on out.
Believe this: tailors aren't just for fancy clothes and they aren't expensive. I take all of my jeans to my tailor and have them hemmed to the exact length of my legs because not a single clothing manufacturer makes clothing that fits my length!
http://www.esquire.com/blogs/mens-fashion/pants-size-chart-0...
So it doesn't surprise me that there's "vanity sizing" in men's trousers. Not even a little bit. This, too, makes for a tough call when it comes to getting dressed. Camel toe or saggy butt? Hm.
(eta: sorry for devolving this discussion into a rant on ready to wear clothing)