OK Machinbird, it's time I do a little learning.
You have a flight control computer monitoring the instruments. How often does it scan them? If it's not too obsolete a design scanning instruments 10 times a second should be quite easy and any "buzz" that might introduce to control operation would be damped by the mass of the aircraft. They might even manage as many as 100 scans a second.
But 10 is a reasonable sounding, to me, bottom end. Am I in the ballpark with this swag? (Scientific Wild A** Guess)
If it is, that means all three probes would have had to plug up synchronously within a fraction of a 100 ms or less scan interval. That means a virtually instantaneous transition from open bore to plugged for all three probes within the same scan.
I'm untutored here; but, two things stand out here as just a little fantastic for my engineering tastes.
Going from open to clogged that fast without literally dunking it in a fluid of some sort bothers me as a concept, especially at an altitude testimony here suggests makes the Sahara Desert look like the Riviera except possibly for very small super cold ice crystals. The plane would have had to fly into a front of just the right shape of a density that would have severely shaken even the loaded mass of AF447 pretty badly. And it must have had just the right shape to turn the trick.
Alternatively, and possible even harder to imagine, we would have all three probes progressing over say several seconds in such perfect synchronism to escape being noticed in the 10 times per second or faster scans.
Based on my supposition of the computer's scan rate the three simultaneously clogged probes scenarios beggar my imagination. And the thought that the pilots would not notice it happening with the sudden penetration of a very thick layer of moisture in some form blotting out the stars "does not compute." They'd have had to be comatose or something.