I'd agree with this - I'm 6'2" and most of my bikes are 58cm, though I also have a 60cm that I ride frequently; on the other hand my CAADX is a 58 and it's probably a bit too big (though ridden often). Items that also need to be considered are top tube length, stem length, and bar width. As said above, try before you buy.
The fixed measurements are the most important of course, a shorter stem does sod all on a 60cm TT when you only have the torso length for a 56. Even with manufacturer sizing variation that's still a TT that's probably ~30mm too long before you set saddle height and fore/aft appropriate to your leg extension and moving you further behind the BB. (Because saddle fore/aft is not used to make big frames smaller)
Then, handlebars add reach, as does their bend, as does the shifter position. It's an absolute minefield and really pi55es me off when people size blindly by height**
**and also tell me I need a bigger frame
*** There are a lot of newbie cyclists these days who maybe don't have the general knowledge of these things, we should be being careful with giving advice, especially when it comes to the large outlay of purchasing a bike.
