Benchmark qualification

Really quick doubt: a median-manager benchmark is, of course, not a good one (cannot be know in advance, thus is not investable and not unambigous). But is it “reflective of current investment opinions”? Schweser says so, but I don´t agree. Because they´re based on a previous year return, from my perspective they are reflective of last year´s investment opinion.

Anybody has other opinion on this subject?

Thanks

per text I believe it says only measurable.