No it's always been around.

It is indeed not in the FAQ, but some supports suspend people who accuse fake giveaway.

A certain support even suspended a user who said "fagg*t"

EDIT : I found it in FAQ

Please refrain from posting any comments accusing the giveaway creator of posting a fake giveaway, and only create a support ticket if the giveaway is fake beyond a reasonable doubt.

Nope. Calling out, no matter what, is against the rules. Maybe you should read them.

I'm not calling out. I am warning him because some support member suspend people who accuse fake giveaway.

And avoiding suspension is enough reason to delete a comment.

you should read the rules, calling a GA fake will get him a suspension.

I think I spotted a fake giveaway, what should I do?

We typically allow all giveaways to run their course without judgement, and allow the giveaway creator a fair chance to prove themselves and to come through with the gift in the end. An exception is when the giveaway creator enters a description that clearly states the giveaway is fake, or if the description illustrates a lack of understanding of how the giveaway system works. Please refrain from posting any comments accusing the giveaway creator of posting a fake giveaway, and only create a support ticket if the giveaway is fake beyond a reasonable doubt.

http://www.steamgifts.com/about/faq
http://www.steamgifts.com/about/guidelines

You're welcome ^^

You're lucky, support haven't noticed you