Although not all accept the Q source hyposthesis, the majority do. In regards to whether crucifixion was mentioned in the document or not, that makes no difference as the Quran already states that it was made to appear as if they had crucified the Messiah. I'm sure some commentators of the Quran have explained that a Roman soldier who had tried to arrest Isa was made to look like him and was crucified in his place. So why wouldn't the Christian texts include the account? It's not like they were told the plan.