First ideas
I have a little bit of experience in the area of mid-air collision investigation.
Firstly, this is not the first, or the last mid-air. Remember that we had a loss of control following a near mid-air in Nigeria with the B727 about 10 years ago. So, if the Boeing crew did detect the Legacy and pulled/pushed/whatever, loss of control is not unknown. We have also had a relatively recent collision with a B737 and a Cessna twin where both survived in Namibia. Small aircraft do hit big aircraft and survive.
I have the T-shirt for the German mid-air collision.
Second, remember that there are slight nose up attitudes to take into account.
Third, the pilot statement is entirely compatible with those I have talked to/read and the theory for detection. You don't see the one you are going to hit. Get a hold of a copy of the old Bureau of Air Safety Investigation report (now Australian TSB) into See and Avoid. A brilliant piece of research.
Fourth, remember the cross wing factor. If you are going to try to avoid, then most pilots bank to turn rather than pull/push for head on encounters, this makes it worse! Draw it out on a piece of paper and you will see that the wings form an X shape and are thus more likely to hit one another.
Fifth, I would make a first guess at the Legacy being slightly lower than the Boeing. This could give you a tail hit on the underside of the wing and the winglet in the engine. However, please remember, this is just an alternative way of getting that damage. The tail of the Legacy just impacts one of the flap drive pontoon aerodynamic fairings, leading to not much damage.
The Boeing looks in pretty good shape, albeit the wrong way up. The engines have gone which is not unusual but would imply more of a loss of vertical stabiliser and then massive yawing, or loss through impact. However, with both engines gone, it may well be more the descent phase. Certainly the 757 in Germany lost the engines for that reason.
The vertical speed of the Boeing does not look great and it was certainly not a nosedive into the ground in one piece. 737 old generation could suffer in flight break up if power dived towards the ground. It just does not look bent enough for that. However, trees can do a lot of deceleration!
Anybody got any idea why the fairings to the front of the main gear are missing? Are they actually there and have just rotated in the accident to leave the area exposed?
The port wing has lost all of the inspection panels but the right wing has not. The port wing appears to carry significant damage, probably in the ground impact and may well have twisted off at that point, whereas the starboard wing in still attached.
The broken link on the left main gear may support the inverted left wing down stop as the gear might be weaker in this direction, when compared with the reverse fitting on the other side.
Ah well, time will tell.