With such serious allegations, and especially being played out publicly in the media, many might think it prudent to not play into that, and instead to keep any evidence for such time as it may be required for one's defence once in the courts, which would ultimately decide on its validity. If he could prove he had been at the assembly, I'm not sure if that would absolutely mean he had a pretty watertight alibi, since I'm not sure what time the assembly was in its entirety, nor whether he could prove the exact time that he was in attendance - for part, or for the full thing, and if part, which part. Also, IIRC, police were pursuing a theory of a 'pedo ring' at the time, which they have now 'all but' discounted. I'm not sure if BS was perhaps included in that 'line of enquiry', but somehow, I am assuming he was included. Perhaps police wondered if he was one of the players in the 'ring'.
I don't believe we have seen any quotes from those who may hold the actual knowledge, since it seems that those individuals have refused comment. I think MSM has only been able to obtain quotes from third hand parties, such as CY, and perhaps other 'unnamed' sources. Police normally do their investigations privately, without telling the media and the public about what the outcomes of their leads are, until such time as the case lands in a courtroom. For all we know, police could have a shiteload of evidence (on him, in general, and/or on other people) that we (and the media) know nothing about. Any lawyer worth his salt will tell a client not to speak to media, and for good reason. Therefore, imho, any silence is not really very telling.