Nether Gold Nuggets to Nether Gold Ore

When I was going through the portal in the Nether, I had 64 gold nuggets in my hand, which I got from the Nether. But when exiting the portal in the Overworld, I suddenly had 64 Nether Gold Ores in my hand...

How to reproduce:
(In Survival)
Go to the Nether
Get 64 gold nuggets
Make a 2x3 portal and light it
Go through portal