[Mr70]

It was probably all about cost & simplicity to themselves.
Why make two design tubes,when one design would accommodate both,where as the earlier would not.As at that time,they were well in the planning/design stages of the 71-72 models,most likely seeing the writing on the wall with the mandatory implement of A.I.R being required on ALL vehicles in the upcoming years,which meant A/C equipped Hydra lifter BB too.
Add to that,I think they pretty much new 99.9% of all new car Hi-perf owners were going to pitch the entire A.I.R. system within one hour of taking delivery anyway,so it getting in the way of adjusting valves would become a moot point.