in case this has not been answered:
It is true that newer versions provide gdb-ia and its sources. Those sources are only included in the installation package and not elsewhere.
The reason for that is the increased complexity providing the sources via multiple channels and the goal to feed back any changes to the original GDB development trunk. So, the newest vanilla GDBs should come with the former contributions* made by Intel (and debuted with the gdb-ia versions).
*: Intel engineers are working with the GDB community. It's the community deciding whether features/contributions are adapted in the end.