Hi Broke My Fibula 5/6inchs Above Ankle 4 Ish Weeks

Hi
Broke my fibula 5/6inchs above ankle 4 ish weeks ago due to fooball (direct hit). Nondisplaced. clean fracture lateral to medial posterior. Doctor put cast on me for 4 weeks then removed he said you can put weight bearing on the leg start. Start off with one crutch and slowley come off it. But i don't understand why he did this as i did see the x ray and it hasn't fully healed. The is still a crack. Only the sides have healed hence a small bulge but the middle hasn't. He said i will be okay in 2 weeks. My question is after 4 weeks immobalised, why take it off and ask me to start walking when i can clearly see a crack in the middle posterior side? Is it because adding weight increases bone density hence bone formation increases? Osteoblasts work more?