Not sure if you noticed the "guaranteed" part of the Neon Beats giveaway. This means that it was a key supplied by Indiegala.
Sure, the game still free, you can activate yourself with the key to get eventual cards or a +1 if it was paid before or you can give the key for free but you still can't make a new giveaway with it.
To be more precise, there is another rule, one that IG probably still follow and no one else, a key won on IndieGala cann't be reused to make another giveaway.
I didn't even know of it, i was made aware by an older user, but it is so extensively ignored that it simply not implemented anymore, the system just prevent you to make more than 1 giveaway with the same key.
I know cause i made a giveaway with a key and some time later won the same key back finding that the system didn't let me made another one.
To make it changing something was needed but it was another time, when Steam clearly stated if the key was still unused it you already had the game and tryed to use it, now it will not do the same anymore so it's impossible to check a key in that case.