my older table has a metal rod beside those planks , tightening it draws everything together and stiffens the structure. the wood had shrunk a tad in length in over 100 years, so I added a shim there.. like at the ends of that missing plank to make up for the shrinkage. . worked fine.. then the bolt wont bow the ends so much.
probably not necessary, never was obviously.
If you added a long Redi-rod there it wouldn't be original , might add stiffness if it didn't get in the way of anything else.. might bug someone that's worried about authenticity.
Wait bit and that jerk will jump in and start ranting that no-one knows anything.. he keeps doing that. I didnt ask his permission if I could post here ;-) he doesnt; like that.