Allay can throw items from the back while it's on boats and boats with chest.
Below is the command to reproduce:
/summon minecraft:boat ~ ~1 ~ {Motion: [0.0d, 0.0d, 0.0d], FallDistance: 0.0f, Type: "oak", Passengers: [{NoGravity: 1b, Brain: {memories: {"minecraft:liked_player": {value: [I; 1080257577, 2089635441, -1481060819, 2104652680]}}}, HurtByTimestamp: 0, Attributes: [{Base: 48.0d, Modifiers: [{Amount: -5.152493655150297E-4d, Operation: 1, UUID: [I; -1825233696, 1969702757, -1155587439, -122379449], Name: "Random spawn bonus"}], Name: "minecraft:generic.follow_range"}, {Base: 0.10000000149011612d, Name: "minecraft:generic.movement_speed"}], listener: {event_distance: 0.0f, range: 16, event_delay: 0, source: {y_offset: 0.36f, type: "minecraft:entity", source_entity: [I; -475332023, 1391348747, -1868134091, -745234627]}}, Invulnerable: 0b, FallFlying: 0b, PortalCooldown: 0, AbsorptionAmount: 0.0f, FallDistance: 0.0f, DeathTime: 0s, HandDropChances: [0.085f, 0.085f], PersistenceRequired: 0b, id: "minecraft:allay", UUID: [I; -475332023, 1391348747, -1868134091, -745234627], Motion: [0.0d, 0.0d, 0.0d], Health: 20.0f, LeftHanded: 0b, Air: 300s, OnGround: 0b, Rotation: [31.177532f, 0.0f], HandItems: [{id: "minecraft:grass_block", Count: 1b}, {}], ArmorDropChances: [0.085f, 0.085f, 0.085f, 0.085f], Pos: [-38.396406529579515d, 64.89999999850988d, -237.05210180581759d], Fire: -1s, ArmorItems: [{}, {}, {}, {}], CanPickUpLoot: 1b, HurtTime: 0s, Inventory: []}], Pos: [-38.396406529579515d, 65.0d, -237.05210180581759d], Fire: -1s, Invulnerable: 0b, Air: 300s, OnGround: 1b, PortalCooldown: 0, UUID: [I; -1107902665, -272612499, -1791583644, -2035167779], Rotation: [-1.0936584f, 0.0f]}
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discovered while testing
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I can confirm this behavior.
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