Was this ever solved?
This is a major issue - both the first day and last day should show as half booked in the date picker. Almost all over our bookings are Sunday to Sunday or Sat-Sat, so that guests leave in the morning and then new guests arrive in the afternoon.
We check this issue from our side seems to be ok.
Please try to disable Enable daily bookings in HivePress > Settings > Bookings > Daily Bookings and check if this issue persists.