I don't agree at all. @
Hriston has provided a gloss; so have I.
I'll do it again:
The lightfoot halfling and wood elf traits—Naturally Stealthy and Mask of the Wild—do allow members of those subraces to try to remain unnoticed in their special circumstances even when watchers are nearby. Normally, you can’t hide from someone if you’re in full view. A lightfoot halfling, though, can try to slip, unnoticed, behind a creature that is at least one size larger, and a wood elf can try to remain unnoticed simply by being in heavy rain, mist, falling snow, foliage, or similar natural phenomena. It’s as if nature itself cloaks a wood elf from prying eyes—even eyes staring right at the elf! Both subraces are capable of being unnoticed in situations unavailable to most other creatures, but neither subrace’s attempt to remain unnoticed is assured of success; a Dexterity (Stealth) check is required as normal, and an observant foe might later spot a hidden halfling or elf: “I see you behind that guard, you tricksy halfling!”
You'll notice that I've glossed "vanish behind" as "slip, unnoticed, behind" - which is along the same lines as the usage that @
Hriston noted, "She vanished into the crowd."