Standards are nice and dandy, real-world-implementations all suffer from bugs, missing features or implement undefined behavior slightly different. So if you want to support an implementation, you need to test it. If there multiple versions of an implementation you want to support, you need to test them all. Any other approach is "it works on X, it might work on Y, but we're not actively supporting Y."

From a practical standpoint, don't you still need to test it against popular platforms though? (If you develop to the standard and a popular browser doesn't support the standards correctly as far as your users are concerned, it is your problem.)

That's a fine thought, until Chrome adopts a new standard in Chrome v46, but half the Android population is still running Chrome v38.

I have no problem with the forks. I have a problem with the fact that they will absolutely not be kept up to date. The article already mentions that new LG phones are being sold with a Chrome fork 4 versions behind the one on the newer LG phones. In time that gap is only going to widen.

And that's just the shiny new features. There are constantly bugs (including security issues) being fixed. What about those?

If every browser vendor fully and correctly implemented a standard on their first try, you'd have an excellent point.

As it is right now, even people that develop towards standards still have to choose between deviating from those standards to support a wider audience or sticking to the standards and turning away users.

Do any platforms implement the standards completely and consistently however?

Hahaha, good one!