Yes, a capacitor across a contact will prevent an arc from forming when the contact begins to open, especially when there's an inductive load like a motor on the other end. Normally there's a resistor in series so the cap doesn't discharge as the contact closes and cause another arc. But if the power is cut from the relay, and the load discharges the cap before the relay drops, then I don't think you would need a resistor at all. And it being a variable variety would allow the mechanic to adjust it in the field until the arc is no longer seen instead of measures and doing math and ordering the needed size.
https://www.te.com/commerce/Documen...36_AppNote&DocType=CS&DocLang=EN the last page of this pamphlet describes what i'm talking about.
Not sure if this is the correct answer, just what I see when I look at the print.