Gertrude the Wombat said;
And don't forget that if any of this cloud is about 3000' you need a much larger gap to descend through than if it's all under 3000'. You can be legally flying above a cloud layer which you can't legally desend through, if it's lots of little clouds without any gaps large enough for you to have the 5km forward visibility you need above 3000'.
You seem to have confused the visibility requirement with the distance from cloud requirement. What you said is along the right lines however, if at or below 3000ft, the desceding spiral through the cloud must remain clear of cloud, when above 3000ft, that same spiral must keep the aircraft 1500m horizontally from all cloud.
It does require a big hole but not quite as big as you thought!
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The law does say that a basic PPL must remain in sight of the surface. Thus a basic PPL could quite legally fly down a 10nm wide valley at 1500ft just above a fog bank and remain legal because they can see the mountains on each side.
What is legal and what is sensible are too different things.
Flying a C170 over an overcast with a base of 1500ft AGL make far more sense than flying 3000ft over a fog bank 200ft thick even if one has an IR!
Regards,
DFC