If this sentence was correct (and I'll try to find time to read the study, and if anyone does, please psot.)
Researchers reporting in The Journal of Nutritional Biochemistry show that reducing oxidative stress, cellular inflammation and improving DNA methylation pathways can extend telomere length and slow the biologic aging clock.
Further down I believe they are talking about what is really happening, delaying shortening, not extending or growing. They call it maintenance. And the Japanese discovered many moons ago that vitamin C levels inside the cell can determine how well telomeres are maintained. Cells with high vitamin C levels can delay shortening by around 40%, over cells with little vitamin C in them.
Telomeres are rather complicated to "grow" and the main way it can happen is via the primary telomere growing enzyme telomerase. (There is a so-called ALT method that some cancer cell use).
Nothing wrong with keeping antioxidant levels high in cells to preclude too rapid shortening.