Semi circular ( E-W) or quadrantal (E-W + N-S) were created for non surveillance airspace and VFR , when under positive ATC surveillance , you can use any level you want .
Also at time created , most airways were bi-directional, which is no longer the case. Capacity is also an issue today , maximizing the use of airspace is the norm .
ODLs were indeed already used widely in the 70,s a s
Chevron said . above. ( I used them myself a lot at the time and in fact always did. )
Finally
pattern is full : no nothing to do with 100 Nm to destination or RVSM , just maximizing the sue of the airspace .