The good thing about how they roll it out is that if they find bugs in the release that they sent out in a few countries, they stop all other roll outs immediately, it happens a lot, most memorable was Android 4.1.1 for the S3, it rolled out in Poland and India for the Exynos, it was quite buggy so much so that most S3s went from 4.0.4 to 4.1.2 and Samsung threw in some Note 2 features.
I've seen the same with smaller updates in the S4 where most regions skip certain releases.
One could ask the same about HTC, Sony and others WRT 5.0. It seems the initial 5.0 is buggy though, we may see most OEMs jumping to either 5.0.1 as Samsung are doing with the Note 4 and Note Edge or 5.0.2, they seem to be waiting for Google to sort out the bugs as 5.0 is a major update, one of the biggest if not thee biggest, so I personally knew this would be much like when Android 4.0 ICS arrived.