I would first note that FDev might be deliberately cautious with this specs, to help deal with the rage of people who try to run Odyssey on potatoes. Since everybody is already raging about the increased system specs, the complaints about bad performance on potatoes might not get too much traction, since that’s expected.
That said, unless there is a lot of optimisation wizardry before the console release (end of PC beta - hi S.! -

), there might be difficulties with potato Horizons users running side-by-side with Odyssey players on surfaces. (Space doesn’t appear to be an issue.)
The way to deal with this might require cutting content - less things to render, so that potatoes can keep up. Since this would cut down the experience for people with modern rigs, it might be that the simplest solution is to “split” Horizons into two parts: legacy horizons that runs on old min specs, and modern Horizons that has specs that matches that of Odyssey. Odyssey could be split the same way.
For a solo player, the difference is that the legacy content is less complex, so that they get acceptable performance. There will be less NPC’s, etc., but the gameplay should feel similar.
But for multiplayer, “legacy” players could only instance with other “legacy” players, as they all have to see the same less complex content. In other words, a permanent split in the PC player base.