Started the same action on Win10TP now and will see this time the HDD is unlocked?! This will may a lot different than on the Win8.1 because I was run already the Re-Install on this HDD, with the result that Win10TP was run, just with locked HDD. OK, the Win10TP was restarted and still get the message: Although, while done the re-install of 10, the Windows Explorer is missing from all menues and need to be accessed via the Search from Charm by using the WinKey +C. As there isn't access to the C Drive, there couldn't be an Shortcut build. Further on: I try to format the HDD now from Win8.1 and Access is denied for that too. So, I'll need to do an Low Level Format of that HDD to overcome that Lock. Will report back later.
Although tested from Debian and the HDD still were locked, no access to it! Some more checks using the Bootrec commands, which all times shown there were success, but in reality didn't worked, the HDD were still in locked stage. Maybe the Bootrec apps has the same problem with W10TP as SFC? That simply could be because of the very early stage of W10TP! OK, no problem, nothing except W10TP and some few apps but data were on it. So finally done the Low Level formatting and now I could use the HDD again as an virgin one.
I would love to see the images though. That is very interesting and it is clear there are some slight differences in Windows 10 from Windows 8.1