One reason that this could be practical is that nearly all EV battery packs are still under warranty (normally 8 years) so if even a single cell goes bad the entire pack is replaced. That leaves a lot of cells which are perfectly good, and could be used in smaller devices.
This particular prototype/concept unit is pretty small - they say it's good for a week, but they're talking about low power demands and assume a 400 watt solar panel feeding it. The storage capacity is only 700 Wh, or less than the capacity of the base single 12 V battery in an Escape. It looks like they are using pairs of 33 Ah Leaf cells, with three pairs in series (so it's a 66 Ah 11.25 V battery), or six 33 Ah Leaf cells in series (so it's a 33 Ah 22.5 V battery).
One complication is that Leaf cells have NMC cathodes, so their operating voltage isn't well suited to RV applications: the voltage of three cells in series is not quite high enough (11.25 V nominal) and when full charged the voltage of four cells in series is too high for use without regulation (16.8 V is charging to 4.2 V/cell). I don't know how they handle this in detail, and all of the articles that I've found are just rehashes of the Nissan promotional material so there is essentially no technical data, but it appears that they don't provide DC power directly from the battery at all. They are supporting only 230 V AC and 5 V DC (USB) loads, so everything must run on one of those sources. For a more typical RV full of 12 V DC appliances, this isn't ideal.