Yes, he said that, but not in the sentence you did quote. Nevertheless, we do not need to understand everything, some things may remain a mistery [sic] 
I think though it only applies to the T1…T3 values, where there is a path or something very similar to such on the ground, and railings e.g. (T1) or assistive measures.
I translate, with machine help:
Also important: What is commonly referred to as hiking and mountain hiking takes place in the T1 to T3 range. Routes from T4 onwards, and especially those around T5 and T6, generally require skills that extend to mountaineering.
I do not see that going against the OSM sac_scale. After all, the OSM scale was badly translated from the Swiss scale of 20 years ago. (Somebody made it better than the SAC own translation though in the mean time.)
BTW: I fully understand why they dropped equipment requirements - people doing such “hikes” do not need advice on that – T6 or difficult_alpine_hiking is a serious hobby: Mountaineering without the gear, in other words: Grade 2 or 3 Scrambling – Repost of new T6 picture
I forgot one point: Somebody said: We must not introduce new highway key values. This is where we are today! Luckily for the mountain hikers, the soon following new highway key value generic path paved their way.
That reminds me of MTB mappers that split hiking trails in a dozen segments. I always wonder – do the stop every 20 or 50 m and discuss the grading? Don’t they just bike through? I see this much less on hiking trails and not to such detail.