The original purpose of spreaders (on masts in general) was to increase the angle between the shroud and mast at the hounds. This means that the rig can be used with lower tension – though there is compression at the hounds instead.
It had nothing to do with mast bend.
I would guess that the original wooden Wayfarer mast was not intended to bend, but I cannot say whether or not it had spreaders.
Unless you can see fittings from where spreaders have been fitted I would be inclined to keep it spreader-less. Spreaders could induce mast bend that your mast was not designed for.
I can see that spreaders could reduce
the wabbles at sea
– but in so doing perhaps induce new problems.
I would suggest that if you want to enhance performance or have a more robust rig then get a metal mast.