To elaborate why such a device is important and who the target audience is now and in the future.
USB storage especially with USB3 SuperSpeed and especially if USB hubs are involved is unreliable as hell. Hardkernel when designing their S922X based ODROID N2 chose to rely on an internal USB hub and as such the usual USB storage drama is happening over there. See here or here or here or here…
So avoiding USB and being able to rely on ‘real’ SATA is obviously a good idea if reliable and performant storage access is part of the use case. Unfortunately all those SBC that feature ‘real’ SATA are either slow as hell or overly expensive. An S922X board on the other hand is faster than Apollo Lake Intel designs and almost as fast as Gemini Lake (compare N2 numbers here in the 7-zip MIPS column with the x86 results at the bottom)
So being able to combine a competitively fast ARM SoC like S922X with PCIe attached SATA at an reasonably low price will attract all those people who search for an energy efficient NAS or micro server today or just a KODI box with a lot of local storage or users who want to explore CEPH on inexpensive ARM64 nodes.
Even if ODROID HC2 is technically underwhelming (old, 32-bit, everything USB3 attached) it’s a top seller for Hardkernel just since it delivers on a complete solution for a 3.5" disk with an enclosure attempt. Now imagine a 64-bit SoC (with ARMv8 Crypto Extensions available), up to 4GB RAM combined with real SATA (so no USB storage hassles any more) and especially the possibility to add 1-3 additional SATA disks in a stackable and inexpensive fashion. Over in OMV forum this question (something like HC2 just with the ability to add one or two additional disks) pops up over and over again and there really is a big demand.
Since dealing with USB and especially USB3 storage is that unreliable and annoying some projects even think about removing support for USB attached disks altogether (being called ‘Removable devices’ in OMV for example, see this proposal by OMV’s core developer). If a future OMV version will remove support for USB this makes the majority of SBC used now as a NAS useless with this software and an upgrade path is needed (my OMV image for Raspberries has been downloaded over 100,000 times within the last 11 months).
Users interested in DIY NAS, home servers or storage clustering search eagerly for something reasonably priced with a fast CPU, fast RAM, real SATA and Gigabit Ethernet. Skip everything that increases BOM costs like Wi-Fi, eMMC or USB PD, keep just the ‘few cents’ components like GPIO header, SPI NOR flash and connectors for displays, camera, IR and USB2. Then let VIMS remain 100% software compatible to VIM3 (just a different DT needed in SPI flash) and you target a different huge market with almost no additional development costs other than designing a stripped down hardware variant and an inexpensive but effective enclosure variant (me being a total hardware noob having no idea about efforts here).