If it's unraring to the same folder as the download, it gens a temp folder right under the unrar folder, then moves the files into place. If it unrars to a different folder, the temp folder depends on whether there are already files in the folder with the same name. If there are, it'll gen a temp folder in the destination and unrar to there.
Funny how this would suddenly crop up after working in a lot of versions prior to 6.50.
I test in windows. I've tested under android (which is basically Linux but, it's Newsbin compiled to run under Linux in android). In both cases, it works. I don't test under Wine nor am I likely to. I don't know how you'd trouble-shoot this under Wine. If it was windows, I'd suggest you run Procmon and watch all the file IO so, you can see where it messes up.
I like that you can run this under Linux, I'm happy to make suggestions and I'm willing to make changes if you find issues but, the trouble-shooting is on you. Find out how to log FileIO, Log FileIO and then tell me what you see going wrong when it unrars.
If other people can make it work under wine then I'd say the problem is your wine version or your setup.