Yeah, stealth being broken is absolutely intentional. Larian desperately wants to give the player advantage on every attack, not only because it largely trivializes connecting with a target but also because it effectively removes the vast majority of debuffs in the game, which impose disadvantage on the player. But, it doesn't stop there! In this game, stealth is the ultimate offensive and defensive strategy. It provides invulnerability at the cost of a bonus action. To the enemy AI, the player ceases to exist when hidden.
Swen said in a presentation that they take great pride in 'broken' mechanics like this, as it makes the player feel 'clever' when they discover them, though I can't imagine why.
