I would say no, but there are a number of details that need to be attended to. Shrinkage considerations can vary by species and degree of seasoning. First tangential shrinkage is greatest. Radial shrinkage is less than tan. by a factor of 2 to 2.5. So if you are using green boxed heart posts you will encounter the least amount of shrink if the free tenon passes thru the center of the post and the girt centers on the post. I would fully house the girt as deeply as practical but I would not hollow the post face abutment with the girt. I would favor not putting pegs thru the free tenon and rely on braces to hold the centered positions. By using free tenons the post will not forcefully pull on the girts. Long sill to girt braces will hold position without being strongly effected by post shrink. If you come from the land of huge timber and have free of heart posts, place the radial grain in girt line to keep the shrink limited.
