( Sorry for delay in answering, I’m fighting this week with a backlog of tasks 
)
This is indeed a known limitation, and high on my priority list. See the roadmap item: Make shadow maps available by a trivial property on light sources. As subtask of it, we need to solve this: “The lights cast shadow maps only within the same scene.” . See also my notes along the lines “we need to improve shadow maps” in news from June 2025.
I know, this sucks big time, making shadow maps (which have otherwise various advantages over shadow volumes) tricky to use.
Stay tuned, we should just solve this I added this thread and your testcase to check then.