In theory, according to my surgeon, there may remain some nerves that still could function even if they do not attempt nerve-sparing.
But I was told thet the general ED med question is separate from the nerves - it is a rehab effort to keep blood flowing so that willy doesn't drop off. You might want to keep him around for shots or to stuff an implant in -
In the fight to get the insurance to pay for them (they pay a little), even the care coordinators admitted that the meds were widely used even in cases where there is no expectation of "natural" erections. But they still did not agree to pay.