i've never heard or read Jay say run less.
so why wouldn't you do additional non running, general strength, technical and neurological work to improve the whole system?
general strength work has a great anabolic affect on the neuro-endochrine system that aids in the production of hormones which enhance regenerati0n and recovery.
and it is necessary now more than ever as PE is all but eliminated in schools and kids don't play in their neighborhoods 4-8 hours a day. instead they play video games on the couch.
so perhaps general lifestyle during the Hadd and Lydiard days addressed the general needs of athletic "foundation" but I don't see that being the case today.