As per title, recipes of the type create:pressing are automatically assigned a default processing time, and then Create complains because this type of recipe does not make use of the processing time property.
Test script: onEvent('recipes', e => {e.recipes.createPressing('minecraft:cobblestone', 'minecraft:stone').id('create:my_test_recipe')}
Resulting warning: Your custom create:pressing recipe (create:my_test_recipe) specified a duration. Durations have no impact on this type of recipe.
Doesn't seem to affect later versions, so I'm not sure it's worth fixing as custom recipes can be used as a workaround, but that choice is up to you devs.