First, I don't work for Adobe and don't speak for them.
I'm sorry you had a bad experience, but I'm not sure it actually has anything to do with Adobe or InDesign. I'm not able to locate any files here on my system, in the Linguistics folder for InDesign CC 2015, or anywhere else in any creative cloud version of InDesign that seem to match your description. I suspect that you may actually be looking at files from a third-party plugin of some sort.
It would help if you told us the exact version of InDesign that you use, and your OS. I suspect there are users her who can help with installing the dictionaries you need.
And the path to where you found these dummy files, along with the actual file names, would be useful, too.
That's actually the file name located in the Linguistic file of InDesign's Plug-in. It's been deleted now since it possessed no usefulness. I've the latest InDesign version. And your username doesn't make much sense.
I've located Dummy.aff and Dummy.dic files related to the Hunspell Dictionary plugin, and I would suggest they not be removed. I'm not able to find anything like Adobe Core Sync.