can't see them under the valve cover so I would not lose sleep over it. I would assume they used both designs.
Just to show you how this could be true about using both designs....I have an original '68 Z28 and the engine has different exhaust manifold bolts on different sides of the engine. Apparently the bolt bins on each side of the engine had different bolts in them and the assembler installed whatever was in the bolt bin. I also have seen different bolt numbers installed on the body assembly other than the ones called for in the AIM. So either the bolt bins had the wrong bolts in them or the assembler installed whatever he grabbed out of the bin, regardless of the number.
So....as Forrest would say "Life is like a box of chocolates...you never know what you are going to get". I think that might describe the assembly line at times.