Entities not keeping their NBTs when spawned from a jigsaw block

Hey guys Is it natural for mobs to ditch custom weapons and switch to their preferred/default weapons when they spawn from custom structures? I tried that one tutorial that allows structures to spawn entities using template pools but the Brute with dual Netherite Axe always switch to gold axe on their mainhand when they generate (also happens when both hands have air) Doesnt happen if theyre from a spawn egg tho Thank you!