I hadn't heard of this before, though it's apparently a cause for sneering or consternation in some circles. My response on looking at it was, "Kind of interesting, but . . . meh."
Steven Dutch has an even-handed article, "Pi in the Bible?" on the subject of 1 Kings 7.23-26, which describes the Molten Sea that was part of the Temple of Solomon. It makes the diameter of the Sea 10 cubits and the circumference 30 cubits, and somebody apparently thought it was a good idea to point out that would give an inaccurate measurement of pi as 3. Says Dutch,
Now the Hebrews were not an especially technological society; when Solomon built his Temple he had to hire Phoenecian artisans for the really technical work. So the author of this passage may not have known the exact value of pi, or thought his readers might not be aware that specifying the diameter of a circle automatically specifies its circumference. In any case, the essential point was the impressive size of the cauldron, and its dimensions were only approximate, because the ratio of the circumference to the diameter is stated to be exactly three rather than the real value of pi . . . [more . . .]
I can tell you right now the ancient Hebrews didn't know what pi was, and neither did most of their neighbors. In New Kingdom Egypt, the scribes had some very clever mathematical formulas to approximate the volume of round grain silos without referring to pi, which they didn't know. It is possible to do a lot of impressive things without knowing pi.
By the way, the Hebrews didn't know the Earth was round, either. Get over it. All the geocentrists, who make me feel cozy and happy rather than weirded out, possibly because I grew up among people of similar reality-denying beliefs and have usually found them to be gentle, decent, hardworking folk, when they claim the Earth has to be at the center of the universe because the Bible says so, are actually basing their cosmology on Ptolemy, not scripture. The ancient Hebrews envisioned a flat Earth with a metal dome overhead holding up a cosmic body of water. It's right there in your Bible. Look it up.
Of course, when I say I feel cozy around geocentrists, understand that, also, when I saw Jesus Camp, I was going "Aww" at the cute freckled kids instead of getting frightened by the horror-movie soundtrack and misplaced references to George Bush. So maybe I'm immune to ordinary fears of religious fanaticism. Or maybe, you know, Jesus Camp was a misleading documentary with a misplaced political statement that tried and failed to link a group of good-natured, well-mannered, and articulate but somewhat eccentric Evangelical children with an imaginary militant political movement.
Whoa, wait, Sungenis actually wrote two whole volumes on geocentrism? Why does a subject like that take two books?
Eh, where was I? Ah, yes. Pi. After introducing his subject, Dutch spends his time dismantling a creationist who goes through great contortions to make the passage give an accurate number for pi. I don't know why Dutch wastes his time doing that, or for that matter why the creationist in question wasted his time, but there it is.
Wow, looking around the Internet, I see that a shocking amount of digital ink has been spilled on this subject. Ah, well, this should make a nice additional annotation in the ol' study Bible . . .