Honestly, I have no idea. I haven't surveyed other titles in this space just yet.
I can say that writing a prep guide wasn't my first concern. I was more interested in writing a book for people who ultimately want a job reading and writing Java code. With that in mind, I think coverage of the OCA objectives is important -- some employers will want to know you've taken that step -- but it's secondary to helping someone develop a solid foundation for learning Java.
Make visible what, without you, might perhaps never have been seen. - Robert Bresson