Typically everything in BeanBay is washed unless I've stated that it's dry processed, wet hulled or pulped natural.
Your guess was correct, that Yellow Bourbon is fully washed.
I would also suggest not getting too hung-up on the processing. It's far better to ty it as a single origin and think how it would work in a blend. Generic "you need dry and wet process" is doomed to fail if the body, flavours and acidity are not what the blend component needs.
When you make notes on a single origin roast include what the dominant attribute was. That will help you long term find the right bean to lift, fill-out or fruit-up a blend.