It seems like I had the EVSEIDs switched for most of the time until now.
At opening, 255701 was AC and 255700 was DC in the Swisscharge app, and that's what was also indicated on location when I visited in September 2024. I didn't see anyone charging to confirm the mapping though.
Sometime around November 6, 2024, the IDs were switched on Swisscharge (observed through IchTankeStrom).
This new mapping 255700 AC, 255701 DC is also what is used in the new Swisscharge app.
Because of the limited parking duration, I have some real difficulty confirming which might be AC or DC just by looking at the live data.