I'm going to disagree with @jhackney1972 on this one. there is a measurable distance between these surfaces.-

the reason why johns solution seems to work is because fusions stitch command defaults to criminally high tolerance-

reset this to a 'still to high' but more reasonable tolerance like .001 mm and it fails, a second demonstration that there is a gap.
the reason this is happening is because you are using a t-spline (form) as your base object. it isn't possible to create perfectly circular structures with a t-spline. the shape collapses a little bit between each of the edges, pulling away from the perfectly circular patterned surface objects.
it is evident that the cross section of the form is not circular if you put a curvature comb on the edge at the rim of the base vase. below your form on the left, and a circle with curvature comb on the right. the comb on the vase should look like the one on the circle-

I also marked the "peaks" on the comb. you will note how they align with the edges in your base form. if you look at your model, your patterned surfaces will also appear close/on the edge at the locations, but somewhat separated between these points.
this is really not a good use for forms. it would have been simpler, and produced clean geometry that behaved the way you were expecting it to, if you had just revolved a spline in the modeling space.