As far as I can tell by reading the code and tracing through the Mozilla debugger, the Table Panel Component (and likely most Panel components) do not use the documented Field.display? optional custom DisplayProcessor. DisplayProcessors seem to be built by unconditionally by code in packages/data/src/field/displayProcessor.ts that does not inspect or use Field.display. I think this is a code bug, or the documentation needs to call out some subtlety that I am missing.
This topic cross references the bug in github: Field.display:DisplayProcessor ignored by displayProcessor.ts or the documentation of Field is wrong. (code or doc bug). · Issue #37237 · grafana/grafana · GitHub, which I believe was closed prematurely.