For those who care to hear my opinion...
A Jones fracture due to an impact is very frequently resulting in a surgical remedy. It all depends on the type of fracture however. A spiral fracture is unstable and results in displacement of the bones, needing surgery to remedy. An avulsion fracture does not require surgery. By all accounts, the mechanism of injury of how Olsen broke his foot, to me, indicates an avulsion.
An avulsion fracture occurs when a ligament or tendon pulls at the base of the 5th metatarsal, creating a fracture at that location. It sounded like Olsen stepped on the foot of a defender, which would have caused a pretty large stretch to that area, and could explain the optimistic timeline for his recovery. If he had been stepped on, or there was a twist that resulted in a spiral fracture, then he would likely be done for at least 2 months. So that's my best guess on this injury. There is zero chance he would be ready to go in 4 weeks if it were a spiral fracture, so that has to be the case here.
So 4 weeks... that seems ambitious but if it's a small linear fracture then that's actually not a bad timeline. At 2-3 weeks enough healing is done at the bone to stabilize the fracture, especially if it's a small linear fracture without displacement. Enough bone can fill that area to strengthen it enough for weight bearing and normal activity. The remodeling stage follows the repairing stage where the healed bone (or callus) is replaced by normal bone and is strengthened up. This takes months. In Olsen's case, there may be no benefit toward waiting 4 weeks or 4 months; the risk to reinjury may be the same depending on the size of the fracture.
The only reason he was out so long the first time was because he had to have his bones surgically fixated, which meant longer healing due to a displaced and/or spiral fracture. The fracture in this instance seems to be minor, not displaced, and likely linear. It's highly likely they place him in a hard orthotic that will minimize the stretch to this area and protect it from further injury after the 4 week (or so) timeline. Don't get me wrong, I don't expect him to be fully healed at week 4. It's just possible it may be stable enough to play on at week 4. These kinds of fractures sometimes don't heal for whatever reason and do need surgical fixation.
I think a 4 week timeline is what Olsen owners can consider best possible outcome of this whole thing. Much better news than the season. To completely write him off for 2018 is a huge mistake. Because I certainly agree he can and will be back. It's just a matter of how limited he is with this the rest of the season, which is a bummer for his owners (can't cut him but can you even play him either?)