Those walls are half-cover. I suspect, if we don't want shots go through, it's only possible when the full-cover is at play.
Explanation (don't believe me): Seems only full-cover objects can block LOS. With the half-cover, depending on how much it's in the path of shooting (raycasting?), it adds to difficulty (->lowers CTH), but seems never reaching 0. So even the worst shooter still has 5% chance (the minimum) to hit a target on the other side. The alternative, full-cover walls, means the other extreme: no LOS at all. The question then is, what is more fun / better for maps with walls?
Your picture is a spot on, because, yeah, with the crouching - visually it really looks like there is no LOS, right? But nope, the game sees target as if standing, got us, haha! Will try necro the front about the visual vs. gameplay inconsistency of crouching in parallel, thanks for reminder!
A few notes in case the essence of cover is still on the table to discuss (very wild observations, probably wrong):
(1) I think from all the half-cover objects on the path between the shooter and the target, only the one adjacent to the target counts. -> Shouldn't at least tall, eg. tree / wall, add to the difficulty of targets behind?
(2) From the log: directional half-cover will influence CTH analogously to as if the target was 2-6 more tiles away. In case of the edge of full-cover, up to 12 tiles away analogy or so. -> Perhaps some half-cover strength tuning or an on-path inclusion (see 1) might be interesting for the map dynamics...
(3) No matter what shown, no crouching is happening next to any cover (see the crouching thread). -> If at will crouching allowed, what about making a combination of an adjacent wall+crouch work like directional full cover but you have to stand to shoot over? Reasons: Visual as explained by Nomad, and possibly tactical trade-off.
Edit: Similar situation in the attachment. Guess where is the target, sister Denisov?