I never heard of this when I was in (grew up in MI) There were parties when bethelites would come, but it was usually more like "sister so and so is throwing a 'we miss you party' for her son" or something of hat nature... the same way to often do when someone first goes off to Bethel. But never did I see an elder or pioneer appreciation day.
OT but we sent a mother's day gift & card to my MIL who is still in. She thanked us and never mentioned anything "bad" about it. I think she knows she isn't supposed to, but enjoys it anyway. She is he type who would go all out for holidays if she could.