I have a few angles to look at the Book 8088 from....
First is it does indeed fill a niche that does not exist in any capacity historically. While all of those passive matrix laptops and handhelds from the 80's are really nice systems for their time, they still don't display in color, only have internal speaker sound, and probably cost as much as the Book 8088 does. The goal of it from this angle is that it's supposed to be like a 1980's laptop computer with a color screen, internal storage (SSD), Adlib sound, and a smaller footprint - as even an original NEC UltraLite has a bigger footprint. It also has a battery that works by modern laptop standards.
Secondly, I think it's meant more as a "Turnkey" solution compared to a vintage laptop. If oyu buy a Book 8088, all you have to do is slap the CF Card in a CF Card reader, transfer over your software, plug the card in, and you're done. Whereas say, I bought a Tandy 1100 laptop like the one above, I might have to recap the motherboard, replace the Hard Disk with a hard to find ancient 40 pin Xt-IDE drive if it even has one to begin with, clean floppy drive heads, clean keyboard and keys, deal with broken plastic, not have a working battery so I'd have to rig something up or find the aprpriate type of battery (good luck) and wire it into the original casing. Not everyone who wants to play DOS games wants to become a Legacy IT Support tech, and not everyone who wants to be a Legacy IT Support tech is an avid DOS gamer either.
And lastly, I could see this as being the future of vintage x86 IBM compatible systems. We already have open-source reproductions of the NES, Atari 2600, Apple II, and others out there to tinker with, so why not a modern PC approximation or several. All of these open source and new retro-projects started out as someone's rough bash-together of cast-off or AliExpress components, so this is not the endgame. What if, in a few years, we get a portable OpenSource Tandy 1000 compatible system with a better LCD and a pointing device, and 4 CPU clockspeeds instead of two.
What if in a few ytears we get a Book 486 that has a trackpad, modern LCD capable of emulating a CRT, and SoundBlaster AWE32 compatible audio, designed to look like an original 1990's product, and the battery life of an original Grey Brick Game Boy!