His hamstrings tendons have probably already been harvested to reconstruct the medial patello-femoral ligament when he had his knee cap stabilisation in May. They do reform.
Don't buy the stuff about his ACL being bought forward by his previous surgery...
He's just been really unlucky with this one.
He will probably have a patella tendon graft anyway for his ACL reconstruction it provides a stronger graft that the hamstring tendons. Depends on surgeon choice that.
There are pros & cons to graft selection and as you say, it's surgeon dependent. It's the same knee which will undoubtedly lead to concerns about the long-term stability of the knee but his rehab will surely need to minimize any lumbar strain. As Pep already pointed out, he will be out for awhile