There are 3-4 spots like this. Want to make sure to discuss with contractor if I should prior to making last payment.
Planks were used in older roofs (which you probably know) which makes me think the decking is pretty old and probably should’ve been replaced with plywood.
There’s really no need to replace the decking unless it’s damaged, regardless of it’s age. It would be an unnecessary expense, and a large one a that.
That vent pipe is PVC which tells me it’s a lot newer than this house so my guess would be that whenever that vent was added or replaced they destroyed that board in the process. Regardless, the roofers should have corrected it. It’s possible they just forgot to circle back to it if this was the only issue.
Plank decking is way better than plywood. You replace solid wood with solid wood, unless a ton of it has been compromised. This should be specified in the contract for the roof. You even get insurance discounts for solid wood. If a roofer replaced my boards with plywood or OSB i’d be super angry.