That's because you take it out of context to debate it.
''Normally, you can’t hide from someone if you’re in full view. A lightfoot halfling, though, can try to vanish behind a creature''
The whole sentence follow the words IN PLAIN VIEW and add the conjonction THOUGH relating to it, which means despite the fact or altough, basically meaning that despite the fact that you normally can't hide in plain view, a halfling can try to vanish behind a creature. This is natural english language 101 and i would assume native speakers would understand that.
Now it appears that having failed to prove that my reading is incorrect, you've resorted to trying to insult my intelligence or my familiarity with English. What you've failed to understand is that my reading is entirely consistent with the full context of those two sentences, the article as a whole, and the ruleset to which it refers. Assuming you
are familiar with the English language, I'm sure you're aware that all you've done above is to restate the ambiguous language of the original article, which still doesn't contradict my reading of it. It may be helpful if you could provide a clear statement of what the above passage means to you and how you think it contradicts my interpretation.
To that end, below, I gloss the passage as clearly as I can, so you can understand how I feel it supports my interpretation. For the record, I understand how the text supports your interpretation, so don't take this as an indication that I think it doesn't. My point is that the language of the Sage Advice article is ambiguous, as are the rules themselves.
Normally [if you are not a lightfoot halfling, etc.], you can't
hide from [not be noticed by] someone if you're
in full view [in a location where you could be seen clearly enough to spoil hiding, i.e. in the open]. A lightfoot halfling,
though [to qualify, rather than oppose unconditionally, what's been said so far], can try to
vanish [not be noticed] behind a creature that is at least one size larger,...