The reason why the B1300 doesnt get updates that fast is because the entire build system and drivers have been closed source for a long time. If the toolchain is stuck on OpenWRT CC, there is not much you can do.

Remember that devs are dependent on the tools from Qualcomm to compile anything in the first place when the system is not completely open source. The open source drivers for the Qualcomm chip used in the B1300 have only recently been deemed stable. When drivers are closed source, they are stuck to a specific kernel version, which in turn means it is stuck to a specific OpenWRT version too.

The MTxxx routers have a similar issue.

Other GL routers that you see lots of updates for have been open sourced by Qualcomm for a longer time, so the devs have the freedom to run the latest OpenWRT and so on.