Fair point about the documentation, but I doubt it's allowed to fail: the 'except AttributeError' is only meant to skip the complete test for builds without support for it, builds which do support it will run the test and will result in a failed build status if the test fails. And yes it's a compile-time option, just like a 100 other features, that's just how it's done in MicroPython and doesn't necessarily equate to 'unstable'.
The reason for it not being enabled by default is probably twofold: code size increase/performance decrease, and it's not a feature which is used often especially not for the majority of targets.
