Why are there two different approaches for integrating gem5 with SystemC?

[Ywinh]

The first approach is src/systemc/tlm_bridge.
This approach uses a heavily modified SystemC library customized by gem5.
The main program entry point is gem5 itself, and it is still actively maintained today.
It also supports gem5 debug flags.

The second approach is under util/systemc/, for example gem5_within_systemc.
This approach uses a mostly unmodified SystemC 2.3.1 library, which makes it easier to integrate with external SystemC modules.
The main entry point is sc_main.
However, it cannot use gem5 debug flags, and its performance counters have become outdated due to changes in gem5.
It also seems to have been unmaintained for quite a long time.

I would like to understand the purpose of these two approaches.
Why are there two separate integration methods between gem5 and SystemC?