Because the regular version's currently free on HB. And free games are taken out of the list of games you can give away until the point value the giver would receive is adjusted to account for that and because the giveaway page would be flooded with things the users could just go get for themselves guaranteed. Many people see that you can't make a GA for the regular version and just choose any other.

However, it is also against the rules to mislabel your giveaways due to how the site recognizes whether or not people are actually redeeming the games they've won and due to the level/point system the site uses. They're not complaining, they're simply warning OP because they can be banned if this isn't actually the complete edition.

Did you read the rules?

You have not received what you were promised. Do not mark the game "received" until you receive what you were promised.
(You may keep anything else you are given as a free bonus.)