Yes, you are getting the previous version based on ScummVM when buying the new one on GOG, but only there.
Without knowing the legal rights situation, it is impossible to say who actually got the money from the now de-listed previous release but I consider it very likely that the money already went to Nightdive beforehand. So, in short, while there is of course a shiststormy thing going on right now, not much has changed. A similar thing happend when the Baldurs Gate Enhanced Editions were released back then.
However, I remain disappointed with the new release. Basically, nothing has really improved, a few things are broken now and there is a smoothing upscaler in cutscenes now that clashes hard with the rest of the game. What people often forget when improving old games with HD textures of whatever is that the athestic is now often no longer consistent. A pixelated character clashes so hard with a smoothed background. What makes this release so shamefull is that Nightdive is usually so good about understanding this. I suspect this is sort of a failed project, they were really hoping to find some old assets and resources after all or doing some code trickery, but in the end all of that fell through and then, at some point, they decided to just release what they had.
But, if you have not purchased the previous release, you can buy this one, play the superior ScummVM-one and ignore the enhanced version.