Do church pianists play from the hymnal as written?

I'm no piano player, but I do know basic block chords and chord progressions. I'd like to learn to play from a hymnal, but I don't know how to start. Since hymnals are written for 4 part voice rather than piano, do pianists play as written? or do they yze the music and rearrange the chords to make it easier? For example, if the b and tenor parts are spaced over an octave apart, would your church pianist stretch their fingers or would they just change the chord structure?...Please be thorough with your answers