Need color matching help

I’m helping my new wife get her old house ready to go on the market. I’ve got everything handled except a spot on a solid wood hickory floor in the great room. The floor is almost 1,000 square feet and in good condition There are four or five boards together covering about 5 sf that have been replaced and left unfinished as a result of water damage about four years ago. No one knows what was finish was used on the original floor ten years ago (I think it’s a poly top coat but I’m just guessing), or if any finish has been applied on the new boards ( I think there has). The original Finnish looks like Poly to me. Using left over hickory cut off as samples sanded with an ROS to 180 grit I was able to get “close enough” color match (yellowing and blending nicely with the original finish) with plain old oil based polly. I sanded all the new boards in the floor with 180 grit using a ROS, and applied the polly. I do think someone applied some kind of clear coat on the new boards so I spent a good amount of sanding to remove any finish that might have been applied only using 180 grit. Well, the unfinished boards in the floor did not respond to the poly like the sample boards did. They remained very white in comparison to the rest of the (yellower) floor. The room is wrapped in windows so I’m sure sun (We are in Southern California) has affected the original finish over ten years turning it a bit yellow. Anyway the patched area does not match, not even close. and I do not want to sand and refinish the whole 1,000 foot floor.
So here’s what I’m thinking/asking. I’m going back tomorrow to really sand the new wood starting at 80 grit, moving up to 180 and remove a good amount of wood, then apply the poly. My thinking is that what ever the finish might be on the new wood it’s probably just some kind of top coat that I want to sand off down to raw wood.
Any thoughts or comments? Advice? Wish I had taken pictures.

-- Ken