The C510 ( and the G1000) is always overshooting the axis. This is known to every single rated C510 pilot.
Thing is , do you treat an approach in icing and solid IMC like a decelerating approach in good weather conditions? Not .. period. Vmo is 250 Kias on the mustang that means that they stormed at Vmo-10 to the loc, at that speed on a 3 ° glide in icing ( engine anti-ice ON) you will have to be idle all the way down, except if you extend the Speed brakes, if you expect to arrive at Vapp at the Threshold.
At that speed and complacency in icing, the outcome is the same, they took a chance and failed. Like night VFR into mountains.. You may be lucky until the day...
I will not trust any report from an Austrian VLJ operator, never. I will trust the LBA findings though.
And from all the scenarii described above, Flaps approach are at 185 Kias, Full 150, Gear no limits..And since they were found up, it is highly possible that they overbanked the plane to intercept, the airframe was completely iced up, and they stalled.
One thing to remember , NO aircraft on this planet can handle SEVERE ICING.. NONE... The only thing to do is to recognize severe Icing...