The player's subpredicate "look_at" partially respects the hitboxes of special blocks.
For example :

• Trying to raycast from the full opaque half part of the stairs in the attached image will stop the ray, however, the opaque part above the hole doesn't.
• Looking from the top of a lectern won't prevent the ray to reach the entity behind.

How to reproduce :

Set up a datapack using :

• A predicate file using the player subpredicate "looking_at"
• A tick function that triggers a specific event (like a playsound) when the player look at the desired entity.
• Place the needed blocks, summon an entity like in the image, and look at it.

Or

• Download the datapack that is attached and install it in a world.
• Place the needed blocks, summon a husk like in the image, and look at it.

summon husk ~ ~ ~ {NoAI:1b}