The bug
The new Piglin Banners are named block.minecraft.banner.piglin.[<colour>] in their description. <colour> Piglin would be correct.
How to reproduce
1) Craft a Banner
2) Put the banner, a dye and the Piglin Banner Pattern into a Loom
3) You will see that the description of the banner is block.minecraft.banner.piglin.[<colour>]
Linked issues
is duplicated by 5
MC-177840
block.minecraft.banner.piglin.(color), Piglin banner.
Resolved
MC-177912
Creating a piglin banner, the color will appear weird
Resolved
MC-178806
Piglin charge banner's design names are missing
Resolved
MC-178942
Untranslated string block.minecraft.piglin.banner.brown
Resolved
MC-179022
The descriptions of banners with the piglin pattern don't display correctly.
Resolved
In the Bedrock Edition the description is fixed and is called "Snout".