They aren't cultivating their own plants. They are just importing them and reselling. They have no control over whether whoever they imported the plants from are treating their plants with pesticides and are covering themselves by saying they aren't safe for inverts.
There is no specific issue with the plant species, so a long enough soak should be sufficient to remove anything harmful. Tropica know their stuff when it comes to plants, so I would follow their directions. Soak for 2 weeks, change out the water twice a week before adding to an aquarium with fish or inverts.
You might be fine if the plants are clean. It depends on how risk averse you are. Quarantining plants as is always a good idea to prevent introducing anything you don't want into your aquarium, the same as its a good idea to quarantine fish. Pest snails would be the obvious one you don't want to accidently introduce with plants, but harmful chemicals is another potential contaminant.
thanks for the information
