A geometric point is treated as a location without extension. A line has one-dimensional extension. A bodily substance, however, is an additional claim about external constitution and subsistence.
Even if the sphere argument gives an indivisible point of contact, one must still show that this point exists as a bodily atom rather than as the boundary of contact.
Example: conceiving the endpoint of a drawn line does not establish an independent physical particle at that endpoint. This is the objection's logical core.