I can see no reason why that spare kit shouldn't fit a 4x4.
Except for the fact it’s a “space saver” with a mere 4.5” rim width and an even skinnier tyre?
Yes, the kit will fit in a 2WD or 4x4 boot, and the wheel bolt spanner will have a 17mm head socket, but the wheel is still far less safe to use to replace a punctured road wheel. Even though such use might be legal, as the ad explains.
As for “Buyer Beware” or “Caveat Emptor” in legal terms. It’s been consistently recommended in here for as long as I can remember (which means since 2015 according to the forum data and probably for some years before that if I looked), to stay away from ads that mention the words “space saver”. Those are a “don’t buy” in Which magazine terminology. Look instead for a 195/60 width and profile tyre on a 16” diameter wheel.
Looking back in this thread alone. Madasafish first asked about buying a “space saver” on 9th Mar, in#9. Respondents immediately warned against that idea, with reasoned arguments against, posted within 24 hrs in #10, 11, 12, 13 and 14. With Snowgood even showing an example of a recommended alternative on 10th Mar. Yet by 23rd Mar the report came back that a space saver wheel had in fact been purchased, against recommendations.
Sorry to sound like a preacher, but I don’t believe it is plausible to expect a sales platform like EBay, Amazon, Gumtree, Facebook, etc. or even the seller, to compensate you for selling you what you asked for. Even if that request was based on mis-informed search criteria. “Live and learn” as you said yourself, perhaps? One choice would be to keep the space saver and hope you never have to use it? Worst case you can still re-sell the purchased space saver on any sales platform. In the same way people sell clothes they’ve worn only once on Vinted.