Not sure why anybody would put a saucer in the freezer.
I see no logic in that whatsoever and know of nobody who does that. I did suspend my saucers on the metal pan supports. They were secure in fact I shimmed the supports in the thickness of two 1/4" washers on each grill strap so they sat very securely but they were also exposed to the direct heat from the coals.
I have a Brinkman pan which I consider to be a much lighter gauge of metal so I do not like to expose it to any amount of heat unless there is water in it. Neither of the saucers cracked immediately but they did crack as a result of the direct exposure to the heat from the coals. I switched to a heavy metal tray and I found it basically acted in the same fashion as the saucer but of course was more durable. I have had similar issues with pizza stones on occasion as well but they have been supported on a grill and exposed to much higher heat.