New Judge, ref the early charging decisions, it is a common practice for the police officer presenting the pre-charge case and the CPS 'Gatekeeper' to opt for the summary only offence in such situations as described here. The main factor in my opinion would be the requirement for the officer to only produce an expedited prosecution file for summary only offences, verses a full file required for the crown court, saving many hours of extra work for both the officer and later the CPS prosecutor. (unfortunately this a reality !).
I fully agree with your comment "and also unusual for a defendant to opt for a Crown Court trial when offered a hearing the the Magistrates' Court", which is a consideration and usually leads to an early guilty plea, however, it is also more likely a solicitor be contacted on the more serious either way offences and well known that they persuade clients to opt for trial at crown (for the solicitors & legal reps benefit).