Haven't seen that but what is fairly common is to see the top flange cut off the fuselage formers and a new and repositioned on riveted in its place. The fit between the fuselage formers and the top skin not being all that great in the early kits (and as far as I know the latest ones, either). The build manual actually called out that solution to the problem and had nice sketches drawn by Van hisself documenting the procedure.
That may have been what is going on here. The top of the former didn't align well with the top skin and the solution chosen was to split the former and move the top up and to splice the resulting joints.
The formers are basically just there to hold the skin in shape (well they do a bit more than that but for structural load calculations I'd assume they were ignored. The skin is sized to carry the shear and the longerons sized and spaced to carry the bending moments of the tail, IMHO. That is another way of saying that I don't think the modification in question is all that big a deal. Only question might be the number and spacing of rivets used to make the splice. You would want the strength of the combined rivets to be equal to the former metal strength in shear in both directions, etc.
A call to Van's might make one sleep better at night?.