“Fast” is subjective. Professional tools like or Z3X Easy JTAG can flash a full firmware in 2–5 minutes over USB 3.0. But no tool labels itself simply “fast gsm” – that’s generic filler.
The term is used by community members on forums to indicate that the specific file has been tested for malware and is confirmed to work for its intended purpose. Usage Prerequisites fast gsm bcm flasher 10033 13 20 repack verified