I think that there may be some degree of inherent bias in the reporting of the experiences of people in the top schools and those in slightly lower-ranked ones. It may be that people who manage to get into the T3 or T6 or T14 schools are sufficiently bright that they don't experience the work as being all that difficult or rigorous, in contrast to students who are not quite as highly capable and are attending schools ranked just below them, who are having to work harder to produce work of comparable quality.
If your assertion about the nature and rigor of the education is spot-on, employers may have found that those bright law graduates from the top schools are perfectly capable of acquiring whatever technical legal knowledge is required for a particular case as the need arises, and may be hiring primarily on the basis of intelligence and the ability to look at situations from many different perspectives, one of the most critical talents in a lawyer.
It's an interesting question to consider.
