Lagat doesnt need the high volume anymore, after so many yrs running, his aerobic system would be maxed. All he needs is to maintain his aerobic work, hence lower volume.
Im sure one would find, in lagats early days, plenty of yrs over 100mile wk.
A more concurrent program, that sounds more like Seb Coe. Very similar to Lydiard, except it being more concurrent.
The principles are the same though, which is pretty cool.