"the OS allows for full compatibility with all Android apps"
The article does not say that. The article mentions an ART target for Fuscia -- you have to build from something. That is approximately 0.1% of the way towards full compatibility. And for that matter you can run Android apps on a load of targets (although far from full compatibility), but that doesn't mean that they're replacing Android.
Google may absolutely replace Android -- they've made loads and loads of mistakes along the way -- but the way people keep arguing it doesn't make sense, using examples that jettison the parts that work well and somehow keep the parts that don't work well (which includes ART, as an aside). And indeed I'm falling into this same trap while talking about Fuscia like it's a kernel, when really the kernel is a small part and they're, at a very small scale, spit-boarding a new take on virtually every part of the system.
Regarding Google distancing itself from the Android name, that's just branding. To quote one analysis -- "Android sounds technical, has baggage, and might be stale". They've had enough missteps that it's an anchor more than a lift, so it makes sense that they stop highlighting it.