If we consider win8.1 TP we have seen lot of new features but for Win10 not many new
Win8.1 we got stable build, win10, more laggy n unfinished product, even existing functionality not working propely(more negativeness)
To clarify this as simply as possible:
Windows 8.1 for phones was at no point ever a beta/alpha/preview, what you got with preview for developers was just a quick hack so that Microsoft could sneak around carriers taking ages to release it for all phones, I repeat, there was NEVER anything less than a full RTM release of windows phone 8.1!
Windows 10 for mobile is in fact a pre release software, and its missing features as its an incredibly early build, temporarily breaking stuff is always going to happen when in development, ESPECIALLY when the update in question is changing so many things
So, let me make this as simple as possible: stop calling 8.1 a TP, it wasn't in any way one.
So with that out there, what exactly are you even trying to say?