Evolving a Pokemon makes it stronger! The point of not evolving a 1st evo Pokemon is to gain the moves quicker than its full evo's for example>>
Oshawott leanrs Hydro Pump at lv 43 but Samurott learns it at lv 62... First evo's gain the moves quicker.
In concern of oshawott missing out on moves..... it appears to me that it will NOT miss on Any.... It still learns retaliate andaqua tail as a minor evo..
Hope I helped.