I already pointed out that there is a version of Gentoo that uses Bionic. You can load Gentoo onto any system you want. In fact, GCC supports Bionic as the default C library, so it shouldn't be that difficult to build any embedded Linux distribution using Bionic if you want. I think ChromeOS uses Bionic too, though I haven't checked.
Also, Android GPU drivers need Bionic (libhybris has a private Bionic). Mer uses libhybris, so Mer relies on Bionic:
Mer uses Glibc as the actual libc that the system uses. They don't use bionic because they think it's great, they use it in a compatibility layer because it's the only practical choice to get driver support.
I said Ubuntu, not Ubuntu Touch.
Dalvik is "fully working" on Ubuntu desktop. It doesn't really matter if a device ships with it or not, since it is trivial to install packages in Ubuntu.
And there's nothing special about Ubuntu that would make package installing any more "trivial" than other distros. Package management is easy in all modern distros.
Gentoo-bionic. Also possibly ChromeOS and ChromeCast, I haven't checked.
So you criticise Android and Ubuntu for being "closed", but endorse a distribution that ships with an actual proprietary closed source software stack developed in secret by a commercial company. Seems contradictory.
The parts that matter are open in Sailfish. And not only open in the sense that you get a big blob of source releases from one monolithical source after every public release. Mer is an actual community project where anyone can join in the development. The software used in the system are community projects too: Wayland, Qt, libhybris, systemd, glibc and GNU tools - all are community-driven software that welcome patches and contributions from regular people. By contrast, Android reinvents the wheel in many cases - they use their own software solutions that aren't compatible with most Linux distros. Ubuntu does the same, with Mir. The fact that Sailfish resembles regular Linux distros much more than Android is a benefit, because it allows you to run any regular open source Linux software on it, which isn't possible on Android.
Of course, these design choices might have been necessary when Android was first made, I don't know. But now they no longer are, and Android is locked into a trap of having to maintain backwards compatibility with their earlier versions. Which means that it will in all likelihood stay incompatible with the GNU/Linux world.
As for the Android compatibility layer, it's an userland application. No different from a distro shipping with Chrome or the Steam client or Virtualbox. It's not a part of the core system, it's not essential for the operation of the system, and it wouldn't be necessary in the first place if Android wasn't made to be so different from other Linux systems - so ultimately it's Google's fault that it needs to be shipped. Maybe if an open source solution shows up that fulfills the same purpose, that can be used instead, but for now it's a necessity for a small startup to use such a software in order to be able to leverage the Android app ecosystem. Either way, it's in no way necessary to ever use Android apps in Sailfish, you can remove Alien Dalvik from Sailfish and it will work just fine without it.