What do pulsating gold quality stars mean?

If you look closely at the GIF (zoom in if needed), on the top right side of my inventory, there are two Summer Spangle flowers that are of gold quality. But the gold stars are pulsating. I've also seen this on some poppy flowers of gold quality.

The Wiki doesn't seem to note this anywhere. When I harvested the spangles, I also received some silver quality ones, but those aren't pulsating like these ones. What does it mean?

This isn't the case with all items. Here is another GIF with a mixture of foraged and harvested items — all of which are gold quality. Again, only the spangles are pulsating.

It's because gold is the highest quality those flowers can reach. Any item at the maximum quality possible will have its star pulsate. For some items that's iridium level, but for some they can't go above gold.

(Source: reddit threads on the matter.)