Mob with custom follow range doesn't seem to work

In Minecraft Java Edition, I have made a custom mob (which is ridden by another invisible mob) using this generator: https://www.gamergeeks.nz/apps/minecraft/mob-generator , and in the Attributes tab I set the "follow range" of both to 50 blocks. In theory, this should mean that they detect and attack any player within a 50 block radius, if I’m not mistaken.

In practice, this doesn’t happen. The mob doesn’t attack until I’m within 10-11 blocks of it. This is the (long) command I used to summon it:

/summon minecraft:skeleton 2877 4 -235 {CustomName:'[{"text":"Suppressor unit","color":"gold"}]’,CustomNameVisible:0b,Health:40,PersistenceRequired:1b,Silent:1b,HandItems:[{id:crossbow,Count:1}],ArmorItems:[{id:iron_boots,Count:1},{id:iron_leggings,Count:1},{id:netherite_chestplate,Count:1},{id:turtle_helmet,Count:1}],Attributes:[{Name:"generic.movement_speed",Base:0.09f},{Name:"generic.max_health",Base:40F},{Name:"generic.follow_range",Base:50F}],HandDropChances:[0F],ArmorDropChances:[0F,0F,0F,0F],Passengers:[{id:guardian,Health:20,PersistenceRequired:1b,ActiveEffects:[{Id:14,Amplifier:0,Duration:99999999}],Attributes:[{Name:"generic.armor"},{Name:"generic.max_health",Base:25F},{Name:"generic.attack_damage",Base:15f},{Name:"generic.follow_range",Base:50f}]}]}

The parts relating to the follow range are in bold. So, why this discrepancy? If it’s an issue of the command just not working as it should, is there any possible workaround?