There is no evidence to suggest that anything else happened. There is only the assumption that McLaren are holding something back simply because of the unusual nature of the accident
The nature of
(the official explanation for) the accident is not unusual.
Not only today Dean Stoneman
had an accident precisely because of the same reason, but also, during a season, that kind of accident occurs many times, although, usually, nothing ends up unexplained.
The reason for all the controversy surrounding Alonso crash, is because the official explanations, the state of the car, and what happened to Alonso
(after the crash), they all do not add up.
That car did not crashed at 150 km/h and his driver did not ended up 3 days in hospital
(and needing 3 weeks for full recovery), that should be very clear to all who saw the pictures of the car after the accident.
I developed a theory, based in something well known by the scientists
(when facing a paradox, the simplest of the explanations is the correct one):
An brain cyst, already removed, is the explanation for the accident.
The
(unofficial) description of the crash, the symptoms, the time in hospital
(only in some cases and considering the latest developments in brain surgery) and the length of the home recovery, match those of a victim of a brain cyst and his recovery after surgery.
That would leave McLaren with little explanations to give, when/if after the all clear from the doctors, they reveal the real cause of all of this.
The only inconsistencies in their press release, would be the cause of the crash
(not the wind, but a, probably partial, loss of conscience) and the reason for the health issues
(not a contusion resulting from the crash, but resulting from the operation).
But that can be explained with the, understandable, wish to avoid speculations about Alonso future and to keep his privacy while recovering.