If they are using the BMW LL12 Spec oil then it seems in line with what BMW do with the B57 in the X5,6,7 etc.20,000km service interval. That’s seems a lot especially on the first service. I’ll be looking at 10,000miles /16k km max service interval for my Grenadier especially for first service or heavy off road use.
That said I’ll be doing my own at 5k after “wear-in”. I figure BMW/INEOS are concerned with the engine getting through warranty period whereas mine is getting the vehicle up to half a million kilometres over ten to fifteen years.