It means that you need to pay 167 CHF to have a look into explanation at https://www.iso.org/standard/13802.html and no success guaranted.
Negative. “The binding of a file‑type program‑parameter is implementation‑defined.” The ISO standards neither prescribe the existence of a
‑Sr processor parameter, nor do they impose
any way how this mapping Pascal file variable ↔ external entity (e. g. a file on disk) happens.
Thus, your conclusion
should have read: “It means the FPC team cannot
properly document this feature.” The wiki, as it has been repeatedly emphasized, is
not the documentation (except for
release notes).
Related: feature request, commit introducing ‑Sr