When the summon command is supposed to add certain attributes to a summoned entity.

How to replicate:

1. Place command block
2. Set command as: `summon parrot ~ ~1 ~ {attributes: [ {id: "minecraft:generic.movement_speed", base: 0.20000000298023224d}

   , {id: "minecraft:generic.scale", base: 3.0d}, {id: "minecraft:generic.max_health", base: 20.0d}],Health:20f}`

3. Place button on command block and press it.
4. A default parrot will spawn even tho its supposed to have a 3x scale and 20 health.

This was also tested in version 1.21 and the command summon the scaled parrot.