Where did the minhag of kashering kiddush bechers for Pesach come from? It seems from the poskim (Rama 451-6 and 451-25) that hagala is only a necessity if there is a concern that it may have been used with hot drink or food. I think it is safe to assume that no hot liquid is used in a becher.
The idea of kashering bechers comes from the concern that they might come into contact with hot chametz items in the sink, which is a potential cause for hag’alah — in particular for matters of chametz, for which we are extra stringent.
The concern of utensils that are glued is that the utensil cannot be safely placed into boiling water, and therefore proper hag’alah will not be carried out. There is no problem for modern utensils, which are comfortably placed into boiling water on a daily basis.