The app should zoom to 100% in that case. It depends a little bit on your camera and how it makes embedded JPEGs. The app should start with the embedded JPEG, and then replace it with the RAW once it loads. If you zoom to 100% before the RAW loads, then it might zoom to the size of the embedded rather the RAW. You might need to wait a few seconds until the RAW loads before hitting the space bar. Which camera are you using?