Unfortunately none of the above helped in resolving the problem, I've looked at the data size and we should be somewhere around 200 Gb.
I've identified the main source of storage (1.1 Terabytes) to be WAL (Write Ahead Logs). This may be due to the way our database instance is configured, though we don't have the same issue for other databases in our infrastructure, so likely it's also related to a detail of how SpiceDB operates. I've noticed the same problem, though to a much lesser extent, appears on our dev instance - garbage collection has been working correctly on our development environment, so a backlog in data due to failing GC can't explain it.
Yet the WAL size on our dev environment is over 5 times the size of the actual data and grows even when the data doesn't