The thing is... you can't know who is at fault in this though.
It's not a situation of who to blame, It's a matter of how much to blame two guilty businesses failing customers.
Yeah, but gog is a distributer. It's not their job to pre-empt developers, else developers won't trust them and won't release on their platform. (Steam could get away with it given their market dominance, but they don't pre-empt developers either afaik).
Gog are in a difficult position here because people expect them to reveal what they know, without considering the implications.
Having said that, yes, it does damage gog and makes gog releases less attractive, but anything else could damage their relationship with developers and publishers who could then crush gog's potential by refusing to release amongst other things.
So I really don't blame gog here, not least because the responsibility to release information on their own products lies with the developer, in this case HG. For gog to release unsanctioned information, or even reveal that there's no information is just not something they can do. (they may even be contractually obligated not to).