How is anchoring 'To Cell (resize with cell)' implemented?

Recent versions of LibO Calc offer the setting mentioned in the subject for shapes.
I tried to find the property used to keep the new setting as its value, but did not succeed.

If someone wants to set/cancel the new property value by a running script he (f/m) would need to know.

From a short glance it seems an UNO API property is not yet implemented for this. Might be worth a bug report.

Done: tdf#124329

Thanks! .