A poisoned Pokémon no longer receives damage outside of battle, and a poisoned Pokémon now glows purple in battle. The poison status will cause a Pokémon to take double damage from Hex and Venoshock. Switching a Pokémon out no longer changes the status to normal poison. Bad poison has dark purple characters instead of white.
Yes I think the same as you it is more realistic with hurt outside of battle poison, But this is just how gamefreak wanted it.