I think I found the underlying issue. Formulas depending on unsynced tables just don’t work, so my attempt to filter one table by another unsynced table failed silently. This is super confusing given that the synced view itself is properly restricted.
The inner workings of this feature are pretty counter-intuitive. I would have expected it to act as a materialized view on the cells and rows without any deeper access necessary. It is also strange to me that the underlying API IAM seems to be single-table specific and that there’s copy implying creating new tokens opens up access to everyone in the doc – that copy should probably be way more detailed.
Anyhow, I guess I’ll just find some kind of workaround, like decoupling some of the directed views or creating an automation-based pseudo-view or something.