Good thing I said it WILL be and not IS the best platform. It was announced like 4 months ago and already has working alphas out. The roadmap has a production release date of Q2 next year iirc. The product is made by iXSystems who are the ones who have been making FreeNAS, now called TrueNAS. They are re-writing the stack of TrueNAS to separate out the storage middleware so that is can be moved from FreeBSD to Linux, in their case, Debian since they merged ZFS codebases so ZFS development is the same across FreeBSD and Linux globally now.
I'm not sure the focus on multiple array pools come into your statement? Multiple array pools, while nice, are not the be all and end all of storage. Unraid is targeted at home and SOHO users, TrueNAS SCALE is firmly targeted at enterprise, so adoption is going to be significantly higher, especially since it will be free for anyone to use. There is a reason Unraid is suddenly pushing hard into the nvidia gpu support after years of letting the community handle it, because that will be a product differentiator that SCALE won't do. Unraid won it's current market share because it's an easy to use docker interface that had pooled drives and supported cache disks and the fantastic community. Without the community apps guy, Space Invader One and devs offering support in the forums Unraid simply would not be in the position it is in.
I would argue there are multiple things, such as NFS4, ZFS and SAS support that Unraid could have done years ago to be in a better position but that's just my opinion. It will be interesting to see what happens when Unraid changes to it's subscription payment model the dude talked about in that podcast and all the USB drives people have licensed eventually die forcing them to subscribe, I wonder if they will - or will they find an alternative platform.