Sadly, no. I did report the bug, though (but had no further communication since). If you want, you can do the same, maybe it will help get a solution faster:
https://www.unrealengine.com/en-US/support/report-a-bug
In my case I wanted to build a filter that kinda acts like the existing spatial grid filter, but optimised for my project (which is cell-based already, so I could make a very efficient custom filter). Using the existing one is okay for now. Putting this here in case this is helpful:
UE::Net::FNetObjectFilterHandle FilterHandle = ReplicationSystem->GetFilterHandle(FName("Spatial"));