As noted above, I had 73 nights, downgraded to Gold (hopefully now fixed). With my Gold card I got a "buyup" offer back to Plat for 50K points. Maybe somehow the downgrade decision is based on whether they think you might blow the points?

But, seriously, how could Plat (vs. Gold) possibly be worth 50K points? Hard to imagine the bonus earning 50K points back, no suite upgrades, and so on. Gold vs. Platinum just doesn't seem to be that different. The Platinum arrival gift is usually water + Milano cookies, value around $3.