Is the age bias in law school hiring a thing of the past?

In my other academic field, philosophy, it is quite common (indeed probably the norm) for faculty to make lateral moves later in their careers, rather than earlier:  faculty in their 50s and 60s frequently take tenured positions at peer or stronger departments.  When I started in law teaching in the early 1990s, this was very clearly not the case:  most lateral moves occurred 5-15 years into a teaching career, with lateral moves by faculty in their 50s, let alone 60s, almost unheard of, except for administrative appointments.  Yet just in the last couple of years, we've seen multiple lateral moves to peer or stronger schools by faculty age 55 and older.  For example:

Lateral faculty moving in their late 50s:  Curtis Bradley from Duke to Chicago; Robin Kundis Craig from Utah to Southern California; Mitu Gulati from Duke to Virginia; Ran Hirschl from Toronto to Texas; Nancy Kim from Cal Western to Chicago-Kent; Kimberly Krawiec from Duke to Virginia.

Lateral faculty moving in their 60s or older:   Naomi Cahn from George Washington to Virginia; Herbert Hovenkamp from Iowa to Penn; Lawrence Solum from Georgetown to Virginia; Gerald Torres from Cornell to Yale.

I may have missed some from the last two years that are also in these brackets, but this is fairly representative.

What explains this change in hiring practices?  I have a couple of hypotheses:

1.  As academic law as an interdisciplinary and scholarly field has matured, there is more appreciation for cumulative scholarly achievement over the long haul, with the result that more faculty with sustained achievement over decades are finding themselves in demand.

2.  The scholarly impact rankings that I started and Greg Sisk and colleagues at St. Thomas have continued--and which US News.com will now produce (and eventually incorporate into their rankings, I predict)--have probably enhanced the value of adding senior faculty with substantial scholarly profiles to a law faculty.  It may just be a coincidence that, for example, Virginia, which underperformed in the various impact studies, has hired a large number of high cited scholars in their 50s and 60s in recent years.