Since there was oil put on the wood, poly probably will not stick. Even after heavy sanding you might have trouble with poly. Fact is poly will not stick if there is any oil remaining.
There may be products available that will remove oil during the sanding process so that the poly will stick? But I am not the expert on that.
As far as light sanding, as you state. I don't think that will be enough for the poly to stick. However, wait for others to chime in...
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