I find it strange people are making threads talking about their creations without at least one Gym to play in it. I mean, without a Gym, you don't have a game. LMAO Even if you get the Gyms in place and no story at first, at least that seems the place to start; you can always change that stuff around later.
The main difference between Progressing Hacks and the Showcase is the length of what you have done so far. To move into the Showcase you need to show that you've created a hack that has a decent amount of progress (generally 2+ gyms or a similar equivalent). Some hacks in Progressing Hacks could show more 'promise' than Showcase ones if they have flashy tiles, amazing scripts, mind-blowing ASM etc, but if they are unable to show that they have reached a certain level of progress in terms of length then they can't leave the forum.
Previous/ other contests (HotM, HotY) have never been Hacks Showcase exclusive; so long as you have a good hack or one that shows promise then it is eligible for being selected. Yes, hacks in Progressing can be abandoned, but that can happen in the Showcase as well.
If you have a good hack that shows promise, shouldn't it immediately qualify for the Hacks Showcase? What constitutes a "progressing" hack and at what point does it leave that status?
One of the rules also invalidates a lot of the hacks in the Showcase anyway - Previous HotY/ HotM winners can't be nominated, which knocks out a good 80% of active Showcase threads right now. It is far better for all involved that Progressing Hacks can be chosen so that the quality of the contest remains high and we don't see the same hacks pop up every few months.