I dount it's intentional, I suspect it's more than no one has needed gstreamermm 1.0 and hence not packaged it up.
Pity though. C is not a good language for writing applications. Sadly there is chicken and egg situation here: only C API is available so people do not use C++ so the packaging doesn't happen. I guess the Debian GSteamermm packagers just "went for it" on the ground 1.0 is better than 0.10.
There's nothing stopping you packaging it up :-)