Yes, it can be hard coded but it seems it should be pretty easy to duplicate what Andrew did for the product type field

There are two approaches that one can use

Since ZEN does not have the ability currently to specify whether a product is new, used or refurbished, perhaps just as Andrew did for product type, we can specify for all products "see description" for the condition field.

It says on Google

Appropriate values include which to means does not mean LIMITED TO so the "see description" should be appropriate

Regardless, the FAQ about required attributes is no longer valid at least according to our contact at Google. All feeds MUST have these fields period.