In that region of that era were all the biggest talents, so what is your point? You can't mix apples with oranges. Or else we could magically put Pogi in the Merckx era and vice versa.Merckx was caught three times anyway.
Consider the opposition.
Many races looked more like a Belgian championship.
LBL 1969: 7 Belgians in top 20.
MSR: 1969: 6 Belgians in top 10.
Amstel 1969: top 7 (!): all Belgians and only two nationalities in top 20.
Omloop Het Volk 1972: 18 Belgians in top 20
Tour of Flanders: 9 Belgians in top 10.
Merckx basically rode against regional opposition.
I don't know how the km are relevant in this story. Considering most riders in Merckx era rode similar full programs, Pogacars domination is even more remarkable. There was very little specialization in the Merckx era.