the egg or the chicken
(Beg your mercy beforehand...)
If the rumour is right and there was an uncommanded "pitch-up":
Which really might have happened:
1 - iced pitots leading tho this pitch-up ?
2 - this pitch-up leading to a reduction higher than 30knots in measured airspeed and (not really sure) consequently to the famous acars message about the probes (and maybe the probes weren't "iced" at all) ?