IIRC you are correct that only a few (maybe those two) said that multiple assailants could be ruled out. Only one, the prosecution expert, said that a single attacker could be ruled out. The rest said that neither scenario could be ruled out.
There it sits. Massei, in effect, has been annulled anyway - and in grand Italian fashion it's not clear what it is about Massei that has been annulled, other than his verdict of guilty.
I think everyone's looking past the obvious at this point.
The obvious is this: from a forensic medical standpoint, it's abundantly clear that this murder is compatible with a single attacker
or multiple attackers.
And the other point to note is that virtually every murder carried out in the absence of disinterested witnesses is "compatible", in theory, with multiple attackers. Even where the victim is killed by (e.g.) a single bullet to the head, a second criminal might have been standing right next to the shooter, egging him on. And that second person would be equally culpable of murder. Likewise, if someone is (e.g.) kicked to death with multiple kicks to the face and body, such an act will almost always be compatible with either one or multiple perps (up to an almost unlimited number for that example, if one's imagination runs wild enough....).
The important thing in the Kercher case is that some ignorant, ill-informed judges came to the bone-headed "conclusion" that since (in their ill-advised view) Kercher would have necessarily tried to fight back no matter what, the very absence of the additional wounds she probably would have suffered in such a struggle means that a) she must have been restrained by more than one person in order to enable another person to inflict the stab wounds, and therefore b) more than one person must necessarily have been involved in this attack/murder.
It shouldn't need to be pointed out that this "reasoning" is as dreadful and illogical as....well.....as the fine mind (also Massei) that brought us the stunning decision that if Capezzali says she heard a scream, then there must actually have BEEN a scream (otherwise why would Capezzali say she heard a scream?)
The truth is as follows: it is entirely possible - likely, in fact - for a person of Guede's build, carrying and brandishing a sharp knife, to have quickly convinced Kercher to adopt a submissive, passive role. This is basic psychology - and it's been used by violent criminals (especially sex criminals) since time immemorial. A larger, more powerful, much heavier man with a deadly weapon can almost always force a smaller, weaker, weaponless woman into submission. The classic "convincer" (though often not even needed) is to tell the victim something along the lines of "If you do what I say, keep quiet and don't struggle, I won't hurt you.... but if you try to fight back or scream out, I'll kill you".
Given that choice, and given the general odds, a very large proportion of women will choose the option of cooperation and submission (since the alternative - the promise/threat of being attacked with the knife - appears disastrously worse. And this is exactly how many rapists, robbers and sadistic killers get their victims to comply - IIRC, the "BTK" killer, Dennis Rader, even got his victims to tie themselves up. They didn't know what his true intentions were of course.
And in Kercher's case, there's zero reason to believe that she must have suspected that Guede was going to harm her - whether sexually or more generally. By contrast, it's easy to think that Kercher might have decided that complying with Guede's orders passively was going to result in him getting her keys, taking her money and other valuables, then maybe tying her up and leaving. And given that she was almost certainly cornered by Guede, she very probably also thought that any attempt to escape - or even get into any sort of struggle - would be futile, and could only therefore lead to a very bad outcome for her. Furthermore, the relative remoteness of the cottage, and the fact that nobody was anywhere near, would have made Kercher think that it was unlikely that her screams would alert anyone (and that even if her screams did alert someone outside the cottage, it would take too long for them to get there or summon help).
All in all, therefore, it would have been an entirely logical decision for Kercher to have complied submissively with Guede's demands. Even when he ordered/forced her onto all fours, she probably thought this was a precursor to being tied up or placed into that position while Guede escaped. It was only (IMO) when Guede undid Kercher's jeans and commenced a sexual assault that Kercher knew Guede's real intentions. And IMO that's precisely when - and why - she DID start to struggle and scream out. Which in turn led to the horrific conclusion.
