It indicates very little for sure. Because platinum can only be LASER mined in METALLIC rings, but Platinum hotspots also exist in Metal-Rich rings where it can be core mined. That's always the mistake people make when they can't prospect any plat: they're in the wrong ring, and/or they never even scanned the inner ring. But as such an experienced miner I'm sure you already knew that.
No, platinum hasn't been nerfed or broken.