Apologies for answering so late, i rarely check the comments here.
You can retrieve your steam key directly from your Groupees account, the same way you did with the itch.io one.
Yeah, I was shown a screen shot of a friends one and he had a steam key icon but mine didn't. It's obviously a problem at Groupees end and I will email them as soon as I get around to it myself. I think it's because I got mine through their trading system and it was probably marked for trade by the original purchaser before the steam keys were added. Looks like a glitch in their key allocation.
Oh! If you got it through trading there, there's no guarantee a steam key is provided, that's something between you and whoever you traded the key with. Sadly, Groupees allows customers to trade the steam and itch.io keys independently (a principle I am not a fan of because it leads to situation like this one).
You sure can ask them just in case. If they can't help, I'll see if i can find you a key (they take a while to generate now and I don't have one on hand right now).
It looks like your right. They apparently have a "reveal this product" option on each game. If it isn't revealed you trade it with all keys but if it is revealed it then shows "reveal key" options on each platform it may have keys for and they can then be set to trade-able individually. I didn't use the trade system very often and didn't notice. Not sure if it should be conducted that way but it is. Thanks for your help, looks like I was mislead.