Madeleine north has an 8% average gradient in the final 4km. Port de Bales is 8.9% average for the final 5km.
This might not be the toughest side of Grand Colombier, sure, but there is plenty about that climb that gives opportunities for attacking before the last 300m. Loads of steeper stretches all over the climb. It's no worse for attacking than, say, Madeleine North or Port de Balès, and a lot better than a lot of bigger but more consistent ascents.
Yes this has stretches all over the climb, but none of them are sustained in the final 6km, which average under 6%, and apparently a 3.5km at 9% inbetween false flats isn't enough either.
If the best 2 riders in the race, one of which has an insanely strong team, decide they wanna sprint for it here, I don't blame all the other guys for not suicide attacking for attacking sake. This is a logical outcome of the race situation and the climb profile, not the riders. The only rider that we might blame is Pogacar, who perhaps missed his best chance to win the Tour today, and I don't really think that either.