The Arrivals Lounge in T4 used to be open later than 2pm; the shortened opening hours instituted a few years ago seemed to be a cost-cutting measure.
I think the title Arrivals Lounge is misleading if the facility is not available to passengers on a number of flights just because of when they land (flights from New York, Boston, Seattle, Los Angeles, San Francisco, Vancouver, if memory serves). Aren't they, too, arriving passengers?