Clarification regarding cover please!

As a new DE player, I am devouring Battle Reports for advice, and have a quick query: A lot of them refer to hiding infantry and vehicles behind other vehicles: do you guys mean ACTUALLY blocking LoS? Or just conferring cover?

If I have infantry behind a Raider, the enemy can see their legs. If I have a Venom behind a Raider, the enemy can see the odd bit of the body.
In reality, even a Raider hiding behind another Raider, perfectly parallel and almost touching, will only be invisible to an enemy standing exactly 90' from the first raider: an enemy a few inches either way will see a bit of the prow or stern of the hidden one.

Do you guys consider Line Of Sight to be blocked in these cases, or just obscured?

Thanks for the Batreps, everyone, and thanks if you can clarify this question for me!

Generally It's just to get a cover save.

That being said sometimes you can hide models from line of sight using a raider (small units of reavers, a venom). Though it's easiest to block line of sight with raiders if you don't place the raider sideways.

For example you could hide a venom from line of sight behind this ravager.