[Hurdy]

Indeed. The Gmail app itself has been able to act as an IMAP client before, but (as it's purely client side) this mode doesn't offer all Gmail features and is quite battery and bandwidth intensive as IMAP wasn't really designed for mobile devices. With Gmailify, the IMAP synchronization happens on Google servers, which also do normal spam detection and categorization, and the phone accesses the data like any normal Gmail account.