Air dried catalpa

Posting this for a friend. She had a catalpa tree cut down in her front yard, and had a local sawyer slab it for her. It's been drying in her back yard under a tented tarp since late last summer. She removed the tarp & found the following:
Attachment 358612Attachment 358613Attachment 358614Attachment 358615Attachment 358616 I'm thinking it's just the pith shrinking up, but it kinda looks like something could have eaten the soft wood between the pith & heartwood. No sign of bugs.?!?!? Any ideas?

Probably not all the damage is due to borers, but there is some evidence of them for sure.