I don't know if this is helpful, but I've noticed that Steamgifts is unable to tell if users own those games. Which breaks some of that site's functionality (which suggests that if it were fixable, they'd hopefully have done it). But by all means do try and work this one out! Then I could point out to them that someone else has figured out how to see who owns those games.
Not so important: Over on SG this means that DLC for games in that status can't be given away on the site, due to the site checking to be sure you own the base game before it lets you enter drawings for its DLC. It also lets folks enter drawings for those games when they already own them. Because a lot of developers use that site to promote their new games, these two issues have been a bit of a PitA over there.