Orange stacks

Possibly going off-topic, but I hope you don't object too much. I have a
question. Please don't spend a lot of time on it, but if you happen to
know the answer, that would be appreciated. The excellent Quanta magazine
have an article about sphere-packing:

https://www.quantamagazine.org/new-sphere-packing-record-stems-from-an-
unexpected-source-20250707

It starts:

"In math, the search for optimal patterns never ends. The sphere-packing
problem — which asks how to cram balls into a (high-dimensional) box as
efficiently as possible — is no exception. It has enticed mathematicians
for centuries and has important applications in cryptography, long-
distance communication and more.

It’s deceptively difficult. In the early 17th century, the physicist
Johannes Kepler showed that by stacking three-dimensional spheres the way
you would oranges in a grocery store, you can fill about 74% of space. He
conjectured that this was the best possible arrangement. But it would take
mathematicians nearly 400 years to prove it".

If I had a grocery store, I think I would stack oranges in a square-based
pyramid, but I assume that a triangular-based pyramid would lead to more
efficient packing. To what does the "74% of space" figure refer, square-
based, or triangular-based? I can't see that they would be the same thing,
but I could be wrong.

Thanks,
--
David Entwistle