It really isn't true at all.
Partially tore my UCL as a sophomore in high school and never required surgery. It only bothered me very infrequently. Occassional pain, some numbness but it never fully tore. Most pitchers that damage their UCL don't completely rupture it and a fair amount will try to rehab and pitch through it before resorting to TJ surgery.
That said, the initial injury was extremely painful and that 3 months of rehab was tough. But compared to the year for TJ, I'll take it.