As I said I own the GOG version myself but not the Steam version. So the PDB files are missing in the Steam release?

Missing ? They are not missing. Because they are already unnecessary. lol

I mean if they are absent. If not it means that the builds are identical on GOG and Steam therefore nobody clould blae GOG in this case.

Edit: Appearently you need to compile the game with some special option set:

"A PDB file contains information for the debugger to work with. There's less information in a Release build than in a Debug build anyway. But if you want it to not be generated at all, go to your project's Build properties, select the Release configuration, click on "Advanced..." and under "Debug Info" pick "None"."

Source: https://stackoverflow.com/questions/3899573/what-is-a-pdb-file

GOG could not know that such files are safe to delete if the devs are uploading their game with said files.

Yes GOG can't know each file in the game but .PDB files are clearly DEBUG files. QA team of GOG at least need to know this . And could check this game's Steam build if actually files are same or etc. GOG is not releasing 999999+ games at a day. It's generally 1-2. But actual problem is even for some games those files are appear in latter updates. And I am remembering in old days even some people were complaining about presence of steam_api.dll in GOG games. But right now people are trolling even serious issue threads too.

If I had not looked it up I would not have known that PDB files are debug files. And what if in some special case those files have the same extension but aren't actual real PDB files so deleting them might break the game? Just keep in mind that i.e. dat files could just be packed archives or really important files with a totally different file format - this could happen with PDB files as well. It's kust an ending not a guarantee that these are actually just debug files as it should normally be the case. Expecting from GOG to compare their build with the corresponding Steam build (which GOG would have to pay for to even access it) imo is ridiculous.

I also cannot take people seriously who are complaining about steam_api.dll files. Often those games were made with Steam in mind. The easiest way to make them DRM-free is probably to change the dll instead of changing the whole game. Also steam_api.dll is only a few kb small iirc. Complaining about this makes me think that people have too much time or don't know what a real probnlem looks like.

With that same reason people are treating those files same with steam_api files. So people actually seeing thread itself as unnecessary but those two things are even not same.

And that is completely correct. GOG should NOT delete files from the installation as long as they cannot be sure that the game will still run afterwards. As I said they cannot be sure to delete PDB files safely in every case and they don't have the option to compare their build to the one available on Steam. That's the way it is. You might disagree but that's the way it is.