Before covid and being in office - "core hours" meant you needed to physically be in office during those hours on almost all days - basically all work days except occasional doctor/dentist/signing-contract-to-buy-house/sick type of situations. And had flexibility to come in earlier or stay later.
In your case it seems to be the same definition of core hours.
Or this "trust to balance their work and life" means it would really be OK for someone to say something like "I'm regularly pick up kids from school/daycare during those last 2 core hours"?
I don’t even want to go into that last sentence.
If you are true about caring about people’s work life balance (which doesn’t seem to be the case), there is only one option: core hours in the middle of the work day. This way you accommodate both people who are early risers and the ones that start up later in the day.