If valid, I don't think it produces "fissile" material, only fusionable material, which is only a problem if one has fissile material to kick-start an uncontrolled fusion reaction.
But I read quickly, and am very willing to stand corrected.
I think you're right. Fission occurs only with very heavy
atoms. Light atoms can fuse to release very large amounts of
energy. The heavy atoms fission to produce lesser (but still stupendous)quantities of energy.