Attached is a simple sphere, with a hole created by boolean difference of an extruded ellipse.
There is an offset cylinder inside the hole, with one end inside, the other end outside of the sphere.

Did a Blend of the sphere hole edge, and the end of the cylinder inside the sphere.
Also did a similar Blend with t he outside end of the cylinder.

I was expecting the surface to be tangent to the sphere, but instead, get a "bulge" at the edge of the cylinder hole.
The bulge can be adjusted with the Blend slider control.
(The bulge does have a nice shape, which I like.)

The question is, why is there a bulge, instead of a tangency to the sphere?
(Flip did not seem to make any difference.)