Mobs aren't dropping their loots(equipments) when killed by fall damage

i noticed with this command

/summon minecraft:skeleton ~ ~10 ~ {HurtByTimestamp: 1980, Attributes: [

{Base: 40.0d, Name: "generic.maxHealth"}

, {Base: 0.0d, Name: "generic.knockbackResistance"}, {Base: 0.25d, Name: "generic.movementSpeed"}, {Base: 0.0d, Name: "generic.armor"}, {Base: 0.0d, Name: "generic.armorToughness"}, {Base: 2.0d, Name: "generic.followRange"}, {Base: 0.0d, Name: "generic.attackKnockback"}, {Base: 0.0d, Name: "generic.attackDamage"}], Invulnerable: 0b, FallFlying: 0b, PortalCooldown: 0, AbsorptionAmount: 0.0f, FallDistance: 0.0f, DeathTime: 0s, HandDropChances: [0.085f, 0.085f], PersistenceRequired: 1b, Tags: ["Snail"], Motion: [0.0d, -0.0784000015258789d, 0.0d], Leashed: 0b, Health: 6.0f, LeftHanded: 0b, Air: 300s, OnGround: 1b, Rotation: [105.2619f, 0.0f], HandItems: [{}, {}], ArmorDropChances: [0.1f, 0.1f, 0.99f, 0.0f], CustomName: "{\"text\":\"Dinnerbone\"}", Fire: -1s, ArmorItems: [{id: "minecraft:scute", Count: 1b}, {id: "minecraft:scute", Count: 1b}, {id: "minecraft:scute", Count: 1b}, {id: "minecraft:player_head", Count: 1b, tag: {SkullOwner: {Id: "542e1c25-333e-4e2a-8da2-27fc12717ddb", Properties: {textures: [

{Signature: "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", Value: "eyJ0aW1lc3RhbXAiOjE1NDQ5OTE5MjczMjAsInByb2ZpbGVJZCI6ImRkZWQ1NmUxZWY4YjQwZmU4YWQxNjI5MjBmN2FlY2RhIiwicHJvZmlsZU5hbWUiOiJEaXNjb3JkQXBwIiwic2lnbmF0dXJlUmVxdWlyZWQiOnRydWUsInRleHR1cmVzIjp7IlNLSU4iOnsidXJsIjoiaHR0cDovL3RleHR1cmVzLm1pbmVjcmFmdC5uZXQvdGV4dHVyZS9kOTMzMTVmZTNkMDA2Njk4NzJmMzY3NWE2ZjIyZjM1OGM3MDNiNDFlYWMzMjM3NzZmNzk0ZWE0MjcyY2E0MjIyIn19fQ=="}

]}}, display: {Lore: ["Skin #418898", "generated on Dec 16, 2018 11:25:27 PM", "via MineSkin.org"], Name: "Reverse Turtle"}}}], CanPickUpLoot: 0b, HurtTime: 0s, ActiveEffects: [
{Ambient: 0b, ShowIcon: 1b, ShowParticles: 0b, Duration: 993333, Id: 14b, Amplifier: 1b}]}