Don't trust the "journalists" expertise on cars ,, try this link to "Kelly Blue Book" ,, it lists the features for that year BMW X5 ,, Xenon ARC headlamps were standard equipment.
http://www.kbb.com/used-cars/bmw/x5/2008/private-party-value/equipment?id=196946
Edmunds seems to agree...
The 2008 BMW X5 is a midsize luxury SUV available in two trim levels: 3.0si and 4.8i. Standard equipment on the 3.0si includes 18-inch wheels, adaptive xenon headlights, cruise control, a panoramic sunroof, dual-zone climate control, 10-way power front seats with driver memory, a power tilt-telescoping steering column, vinyl “leatherette” upholstery, the iDrive electronics interface and a 12-speaker sound system with two subwoofers, CD player and an auxiliary audio jack.
I stand corrected!
http://www.edmunds.com/bmw/x5/2008/#fullreview