That math works for Shinzon's youngest age, making him about 22 in Nemesis. A bit young, esp. since he served with distinction in the Dominion War, so he was probably created earlier. Picard was already considered "a legendary Captain" during his years on the Stargazer. The TNG novel "Death In Winter" hypothesized that the Romulans were cloning many Starfleet Captains, and got Picard's DNA at the Crusher's wedding in 2348.
I always wondered about those lost years of Picard's, just like the missing ones between TOS movies 5 & 6 (5 years). No one's written much about those time periods.