I fixed my roof a few years ago, and have part of a roll of tar paper sitting in the basement. I’m now re-laying some hardwood flooring. Can I use that leftover stuff as underlayment, or is there some subtle but important difference between “flooring” tar paper and “roofing” tar paper that means I ought to go buy some other product?

(If it matters, the house was built in the 1940s and uses materials typical of that era. I’m just doing repairs/small modifications, so I’m patching in like-for-like stuff.)