I downloaded it and looked at Estonia's flag. It's all wrong. I don't personally care, it looks close enough, but some people might take issue with this.
The ratio is 3:2, but the correct ratio is 11:7. The colors are wrong, both the gradients and flat versions. The correct RGB colors are well defined. [1]
It's a set of flag icons for the web, it's not to hang off the government building.
If we did exact aspect ratios for every flag they would all be different and look shit. We tried to be as exact as possible with colors and shapes, if they don't work for you guys or are not close enough then you don't need to use them.
Not aimed directly at you, just at anyone who doesn't find them precise enough.
If you check out the flat flags the colors are exact, obviously the styled ones have subtle shadowing etc, and are probably out by a very small margin.
I checked out Estonia from above and the colour doesn't match the examples on Wikipedia. I've also checked out the Australian flag, and it's eyeball-different - the blue in the real flag is closer to navy blue. The blue should be #002B7F, but a colour picker tells me that the 64x64 flat flag has a blue of #003399.
It's not a big problem in my opinion - no-one should be overly hung up about minor anomalies like that for web icons - but it's not true to say the colours are exact.
The ratio is 3:2, but the correct ratio is 11:7. The colors are wrong, both the gradients and flat versions. The correct RGB colors are well defined. [1]
[1] Colors and ratio are defined on this page http://valitsus.ee/et/riigikantselei/riigi-ja-omavalitsuste-...