I wouldn't get too excited about this announcement. It's only possible to use bash and WSL isn't setup for running a full Linux OS complete with it's own GUI. It can be done but is not at all easy to setup.
For that you are still better either running your intended distribution natively as a bare metal install or in VM.
So to say you can download and run any Linux OS from Windows Store is stretching the truth somewhat and blatant PR spin. Technically it is true but the limitations are quite extensive. The whole concept was initially just to enable admins and developers to run terminal commands cross-platform
yes indeed, it's pretty much a load of PR bull. essentially you'd just be able to use minimal install without gui and choose packages which run from bash only. the equivalent would be offering an ms powershell environment in Fedora and stating Fedora now supports installing windows from GNOME Software.