Just to be sure I understood: Your concern is the potential need to change a reservation and inability to do so when the travel agent's phone lines are overwhelmed?
The nightmare scenario I want to avoid is being at the airport with a human in front of me willing to help me adjust my ticket to get me home, but being unable to do so because the airline doesn’t “own” the reservation and won’t take it over.
That’s why I stick to “utility” hotel bookings only on the portal. If I show up for 1 night at an airport hotel, even if the portal provider mangles my reservation badly I can likely still bail myself out by booking (albeit at a much higher rate) on the spot to still have a room for the night.