Pretty much every single sound Lego Bastion makes is far quieter/less noticable than regular Bastion skin’s sounds, which allows them to go unnoticed for far longer and gives them a distinct advantage.

His shooting? Far quieter, seriously it’s pretty much silent…
His turret form movement sounds? Far quieter, almost unnoticeable mid-fight.
His footsteps? Far quieter than regular bastion footsteps.

Any skin that has different sounds should be switched back to their default sounds in competitive matches otherwise they are unfair. Simple as that.

You train yourself to listen out for certain sounds associated with certain abilities/heroes, and when that hero has a skin that changes those sounds entirely, you no longer notice them. That isn’t fair.
There are a lot of skins this applies to, but the Lego Bastion skin is by far the biggest offender, because it turns a hero that is usually loud asf into an almost silent ninja character. It’s beyond stupid.