You'll see that the first sentence says "one of the mechansisms". There are others, including a heritable eccDNA replicon which can possess over 50copies of the gene; its function is not yet fully understood, but there is evidence of this mechanism being transferred via hybridization.

Besides, the mechanisms of HGT are "natural", and genome engineering is not a requirement. What I'm referring to is an increased resistance in palmer amaranth which is subsequently bestowed upon other amaranth species

Glad you found it interesting enough to read about though. It's fun to see my colleagues' work being referenced