Here is a photo of Red elm,
Ulmus rubra, from Keim wood supply. The issue I have is the ulmiform pore structure is almost always seen in any cathedral grain layouts. See the wavy pattern below? You can see it below Big Ry's thumb as well. However, this pattern is not always the case as seen with several samples on the hobbithouse site.
View attachment 294469
From the sawyer's point of view, they were thinking 'honey locust'. Slippery elm gets platy bark when it reaches larger diameters (16"+). The color of the bark can also be similar between Honey locust and Slippery elm. Both can have a 'piss-like" smell when milling. Next I think of location. Where was the tree harvested? When looking over USDA FIA tree density maps, Slippery elm is far less common in the eastern portion of PA. It is planted as a street tree sometimes, but quite rare in the wilds until you get closer to central PA.
Still thinking about this one.