Yes, they are excellent, I know several of the docs from sports medicine meetings.
If it is an overuse type of problem (and obviously I don't know the specific circumstances) it could certainly occur in either leg. Spending time on crutches, then without impact loading, the bones tend to remodel to adjust to the reduced workload. That's why it's important to ramp up slowly. An Achilles repair may be solidly healed, but it takes time for bone to re-build back to the prior level of strength. Also, with an Achilles there are alterations in gait that have to be corrected to get back to normal, which can increase stress on either leg depending on the gait disturbance.
That's a long way of saying yes, it can easily happen, and I'm not terribly surprised. Sports docs go to great lengths to try to minimize these biological issues, with early ROM and mildly stressful activities as the injury allows. And yet still they can happen.