For the record, 3 means
"Avalanches may be triggered on many slopes even if only light loads [2] are applied. On some slopes, medium or even fairly large spontaneous avalanches may occur."
in turn a light load is defined as :
light: a single skier or snowboarder smoothly linking turns and without falling, a group of skiers or snowboarders with a minimum 10 m gap between each person, a single person on snowshoes.
That's no more and no less than HAT described :
We're concerned because it can collapse with the weight of just one skier - that collapse can then release a slab avalanche under a person's feet or even on a steeper slope above them. Météo France is warning about this layer
Which is just how level three is defined, the weight of one person can cause a failure.
There is a poor layer in the pack but that's obvious, it wouldn't be risk three if the pack was consolidated. The significance of the layer arguably isn't anything to do with day to day risk, it's highly questionable how long it's going to take clear which is the concern. Most high risk levels are associated with recent snowfalls and clear as the top layer consolidated with an already consolidated base, that's not happening and that's a concern.
So, right now the snow's unstable and poorly consolidated but not incredibly dangerous in the scale of these things, it's just holiday time and you tend to see these incidents a lot. ie, these incidents are a lot more to do with human factors than they are some quality of the current snowpack