Non-Real Time Data Augmentation for CNN Classification. What are the drawbacks?
Yes, they are mostly referring to real-time data augmentation.

It is not said that raw images are never used. Actually, it depends on what kind of data augmentation function you are using. Original images can either be kept intact or distorted.

Data augmentation si done real time pretty much 100% of the times for the following reason: data would be too big to be stored on your hard drive. Even the smallest image datasets could take hundreds of GBs after augmentation.