It'd be great - if in the game description - if it mentioned that the game will be using DOSBOX vs SCUMMVM.
The reason I say this is - because I am noticing in several SCUMMVM versions of what GoG is releasing - they're not releasing ALL of the game files. Rather, making some custom start through SCUMMVM where specific game files are not included, thus making it impossible to play through DOSBOX if that's your preference (say for example, if you want to record the game footage through DOSBOX which ScummVM, for example can't do - or because you have an actual x386/x486 that you want the authentic feeling to play on!)

I'd be less inclined, myself knowing if it's ScummVM that I am purchasing a game, that doesn't include all the files.

I'd made a WISHLIST here on GoG about ScummVM games including all files (https://www.gog.com/wishlist/site/for_dos_games_if_theyre_scumvm_also_include_original_files) and has so far, 498 upvotes - which seems like, I am not alone in wanting ALL of the game files I am paying for so I can choose to play the game with my own desired experience.

I've noticed some of the games I have in my library that have been "updated" have also gone the route of ScummVM and removing files, when previously it'd been DOSBOX. (Thankfully I keep all my old files).

So games marked with ScummVM would allow folks purchasing this game that not ALL game files may be included.

There may be a reason for that:

https://forums.scummvm.org/viewtopic.php?p=88181&sid=8c8ec971a4b2a7eec14fc8903c84aea7#p88181

I had long voted for that simply because I find it completely absurd that the only way for someone who buys a DOS game from GOG (expecting the DOS files to remain intact) to re-acquire the deleted files is to be driven to Abandonware sites...

I completely agree about the abandonware part and how ridiculous it is.
However, you shouldn't expect anything from GOG files. Very few old games on GOG have files as they were in the original game. They use third party software, hacks, and even warez cracks to make games run on modern computers.

I have never understood why it's necessary to remove the original exe files, as they take very little space, but GOG never promised to offer those nor did they ever pretend to be preserving games in their original format.
I really wish they would, but, well, they just don't.

The game page says if it uses DOSBOX or ScummVM, under the System Requirements, but not WHICH games do.

Ah ha, this good to know! I wonder if they update these as they shift more games to SCUMMVM.

I just checked - and I see CODENAME: ICEMAN shows as using ScummVM. I know most of the games used DOSBOX originally - and had all the files. Since switching to SCUMMVM, they're missing files.

@PixelBoy and @AB2012 - I agree, about going to abandonware sites for the files is not the answer. (I just made the Wishlist to include ALL files - I can't help what people comment).

And yes, they use "hacks" for the game - for example, bypassing some copyright protection that some games have. But at least the files SHOULD be there so someone has the option to choose between SCUMMVM... or DOSBOX... or on a native x386 (or x486 or whatever).

Considering how small these games are (old games) file size wise; it certainly isn't because of bandwidth (when they have games like Pillars of Eternity) that are MULTIPLE GBs in size - most of these old games probably aren't more than 5 to 10MBs total.

And sure - they don't promise to give you the exact game.

But imagine buying a shelf you need to put together. And nowhere on the box does it say you need to buy a specially sized Hex Key Allen Wrench. So you open the box, take out all the shelves, and all the screws - and discover - "Well, damn it. I don't have the Hex Key Allen Wrench needed!" When to include it is probably just easier for everyone! :)

GOG would naturally only support their installers (say it's a SCUMMVM game) - so if someone tried to use DOSBOX (assuming we had all the files) - then GoG would naturally and understandably be like, "That's on you to figure out. Use the package we provided and we can support it. The other files included that allow you to run it on DosBox or Natively are not supported by GoG."