When you summon a zombie with a high follow range (55.0, 100.0, etc) it seems to retain it's vanilla value.
Reproduce:
1. Summon villager
summon villager ~ ~ ~ {NoAI:1b}
2. Summon zombie 75-100 blocks away
summon minecraft:zombie ~ ~1 ~ {ArmorItems:[{},{},{},{id:"minecraft:diamond_helmet",Count:1b}],Attributes:[{Name:generic.followRange,Base:100.0}]}
Notice that zombie does not track villager. It will only start tracking from vanilla distance.
This works fine in 1.13.2
Duplicate of MC-145656