[throwaway_yy2Di]

Of course. An advanced civilization with engineering sense wouldn't waste precious building materials on thousands of kilometers of planetary bedrock.

(And that's to say nothing of that area/volume ratio, what that implies for radiative heat rejection!)

[sharpneli]

And a termite might think that an advanced civilization would never spend tons of valuable vegetable matter for purely aesthetic reasons.

It's all about the relative abilities. It's not completely unconcievable that some might transform planets the way we build funny houses, even if they are 'waste of precious building materials'.

[arethuza]

I seem to recall that the Culture does regard planets as being rather wasteful of mass - much more efficient to build an O.

NB I'm sure some Culture ships have probably built planets in idle moments - just for the hell of it.