The Specialized fit tool is pretty good, but it doesn't really account for variations in drop/comfort. If you're flexible, you can go one size smaller, if not so, one size larger as the bar to saddle drop changes - more drop in the smaller size. I was between a 49 and 52, went with the 49 but it'll be on the edge of what I can ride at 65.
Don't have the bike yet; latest drama is that I ordered with a 11-34. They built with a 32. I said ok, just throw in a chain as I have a 34 but will likely need to resize. They respond, well, Wheeltop max is 32. Sent them a screenshot of the Wheeltop specs (max 36) but told them don't bother, I'll eat cassette and chain, just ship already.