Hey @cosmick thanks for all of these details! This is currently by design, although we've gotten quite a few requests to enable hiding by currentSourceRow, so we might end up supporting this in the future.
The thinking with not supporting currentSourceRow in the hidden field was that it could be confusing to end users if buttons aren't visible on some rows and are visible on others and they can't see the logic. The workaround is to use disabling, which would give more context to end users