When using the Field Service Schedule Assistant (with travel times), the filter options only let you set a filter for the Start Time and End Time.  However, with travel times enabled, the Start Time is when the resource begins travelling (not the start time of the booking/appointment with the customer).

For example, if a customer is on the phone and requests a 10am appointment, there is no way to easily get suggestions where the appointment time (Est. Arrival Time) is 10am.  A user might open the schedule assistant and enter a Start Time of 10am - this will display results where the resource begins travelling at 10am.  So if the travel time is 36 minutes, the assistant recommends an appointment time (Est. Arrival Time) of 10:36am.

Of course, there are ways to update this after the assistant makes the recommendation, but that causes extra steps and there is a risk you are now violating certain restrictions (work hours, other bookings, etc.) that the assistant takes into consideration.

I would suggest adding the Est. Arrival Time as a filter option (along with Start Time and End Time) or simply replacing the Start Time filter to drive the Est. Arrival Time.