When should i use stereo combined panner?

The stereo combined panner really confuses me. Is this for stereo tracks only. What is the use of this panner.? Is it ok to use default balance panner for stereo tracks?

to make stereo signal a bit less wide.
For example, you have a stereo synth with overprocessed with a stereo enhancer, you make left around -80 and right around +80 and issue may be gone.

Or to place a source within the sound stage. For instance to have a stereo piano on one side of the sound stage rather than spread unnaturally right across it, similarly with drums to avoid a kit being over-wide.

Using the balance panner will alter the balance of the L and R components within your stereo signal, whereas the combined panner will allow you to alter their placement without affecting their relative balance.

When mixing band material, I find a useful starting point is to visualise a little set of musicians who have set up their gear on my meter bridge just as they would on stage, then align the basic mix to their relative positions on that soundstage. The kit roughly central and occupying about a quarter to a third of the stage width, stero guitars toward the L and stereo keys toward the R, for instance

I use it to mono everything and widen at end.