Upper class
is Virgin's 'first class' product, but the pricing is comparable to BA Club class - eg £3500 London-New York return, while BA First is £6600. So TBS's comparison is very valid (and useful) since the choice for most travellers is between BA Club and Virgin Upper (I know which one I'd pick).
It is, by the way, increasingly tricky for 4-class airlines to keep a gap between 1st and Club (to justify the 100% premium for 1st class - similar comments apply to Club and WT+) while competing with the Virgin offering. See
Air New Zealand merges first and business classes - and I bet they won't be the last!