Is ghusl from janabah obligatory for someone who does not ejaculate semen after foreplay or similar acts without penetration, due to prostatectomy?

Ghusl is only obligatory upon the emission of semen to the outside of the body. So, if one feels its emission but then holds it back, ghusl is not required of him. This is the view of most jurists, and their evidence is the saying of the Prophet, peace be upon him: "Indeed, water is from water," and "If you gush out water, then perform ghusl." If anything of semen descends, even a single drop, ghusl becomes obligatory. Similarly, if it is confirmed that semen mixed with urine has been discharged. However, if one sees nothing and does not feel its emission, ghusl is not required of him.