I believe the operation is much simpler than you surmized.
Pressing the "This is Spam" button:
1. moves the currently selected message to the Anti-Virus Quarantine
2. records the sender in order to 'capture' future messages automatically

There is no magic. And I would offer, to the original comment about the time it takes when you "press the button". That is an investment. Every future message, from that sender, will be automatically removed. Consider the time as 'training' your software.