I'm using version 1.5.36 on my Paper 1.21.8 server.
When piglins approach stacked gold ingots, they only take one ingot at a time, even if they are not stacked.
I noticed that when piglins pick up ingots at the same time, only one of them actually get one. The others just canceled their actions and made no further attempts.

Then I disabled gold ingot stacking and reloaded the plugin, piglins instantly took all gold ingots.