Well yeah, precomputation is downside, but you have to offload some calculations somewhere.
At least after precomputation you can (in theory) add arbitrary amount of dynamic lights, they all can contribute to GI, with arbitrary amount of bounces and don’t have any bug impact on performance.
Where with fully dynamic solution, you will kill user PC, or with light maps, you would wait ages for lighting to rebuild.
But besides that. Looking at Enlighten demos, you wouldn’t need to add big amount of lights in first place. On where it makes (realistically) sense.
DRT is very similar to what Geomerics use.