Just looked at mine and I don't see one - the rear sub frame is different on the 260's and it has the track pack with LSD, stainless lines and bigger brakes with Pagids - but no rear anti roll bar.
And mine does have Advan A048's.
The European versions offer some different features on what is called CUP 260 instead of Sport 260 here in the US. The CUP 260 can get fuel and electrical cut off, extinguishing system and a type of roll bar support that ties into the harness bar. I haven't read anything about an adjustable rear anti roll bar on the European version either. I think the magazine/site made a mistake.