Why Deutschland was not literally a pocket battleship

Is it fairer to call Renown a pocket battleship than the Deutschland class?

No. Renown is a battlecruiser, while the Deutschlands are heavy cruisers whose dramatic label came from the press.

The famous 'pocket battleship' label was press rhetoric rather than a sound classification. Gun caliber alone does not determine whether a ship is a battleship, battlecruiser, or heavy cruiser. The Deutschlands lacked the armor, hull density, and tactical expectations of a battleship and were supposed to avoid stronger cruisers. A ship that must run from heavy cruisers and cannot escape a true battlecruiser is better understood as an unusually armed heavy cruiser.