Perhaps the width of the metal accounts for the discrepancy. The diameter being the outside diameter and the circumference being the inside circumference. Perhaps.
Perhaps as this was a known issue, π = 3 was considered an acceptable standard for illustrative purposes.
He made the Sea of cast metal, circular in shape, measuring ten cubits from rim to rim and five cubits high. It took a line of thirty cubits to measure around it.
1 Kings 7:23 NIV
Outside diameter is 10 (cubits)
Inside circumference is 30 (cubits)
Therefore, inside diameter is :
30 ÷ π ≈ 9.55
Outside diameter minus inside diameter :
10 - 9.55 = 0.45 or roughly half a cubit.
This difference is shared equally between the two widths of the material at the two brims.
The width of the material is therefore about a quarter cubit.
It was a handbreadth (טֶ֔פַח) in thickness ...
1 Kings 7:26 NIV
Perhaps the best clue we have as to this :
All these structures, from the outside to the great courtyard and from foundation to eaves (הַטְּפָח֔וֹת), were made of blocks of high-grade stone ...
1 Kings 7:9 NIV
Most modern translations consider this to be the coping.
While no doubt the coping was stone, this is without doubt a reference to the corbelling, which with supporting column, resemble a raised forearm with upward facing palm, hence "hand".
Or alternately, a raised forearm with clenched fist. Both having the resemblance.
A common definition of a cubit is the distance between the elbow and the index finger with an outstretched hand.
However, with a clenched fist, a handbreadth, is a quarter the distance between the knuckles and the elbow which squares with the difference between the width of the bowl and its diameter.
This fits but we simply don't know the bible cubit or handbreadth.
However, at the end of the day, this is not instruction from deity, it is a record of what was built by Solomon according to those that measured and recorded it.
It took Solomon thirteen years, however, to complete the construction of his palace. He built ...
1 Kings 7:2 NIV
A record of the work done, no doubt by stretching rope across one of the diameters (watch out for those chords) and then running that rope around one of the circumferences :
He made the Sea of cast metal, circular in shape, measuring ten cubits from rim to rim and five cubits high. It took a line (קָוֶה) of thirty cubits to measure around it.
1 Kings 7:23 NIV
Any so inclined ancient artisan could determine that the circumference of a circle was slightly greater than three times its diameter.
Sure enough, this was known long before Solomon.
Rhind Mathematical Papyrus
The Rhind Mathematical Papyrus (RMP; also designated as papyrus British Museum 10057 and pBM 10058) is one of the best known examples of ancient Egyptian mathematics.
It dates to around 1550 BC.
The fractional term 256/81 approximates the value of π as being 3.1605..., an error of less than one percent.
https://en.m.wikipedia.org/wiki/Rhind_Mathematical_Papyrus
Not co-incidentally this corresponds with the chronology of the servitude in Egypt.
No doubt this also a great matter of interest some 430 years prior when Joseph was in charge of the pantry for the biblical world.
Calculating the volume of grain in a cylindrical granary, would have been a big deal before, during and after.
There's record of other ancient civilizations grappling with π - it was a known issue.
It's more than reasonable that either the hebrews were aware of the intellectual matter, or the practical matter, or both.
It is what it is.
There's half a dozen ways to slice this and end up in the same place - that π was a known issue that does not derogate from the inspiration of the bible.
The last laugh.
As π is an irrational number, there is no capacity to represent it numerically, perfectly, then or now.
In that sense, 3 is just as valid as 3.141592653 ... both imperfect.
The scribes knowing this, and knowing the price of papyrus, shouted "3" and knocked off early to hang out at the temple, smiling amongst themselves as they passed the metal sea, they alone knowing the choice they made that allowed them to save time and money but to also not compromise perfection.
Perhaps the width of the metal accounts for the discrepancy. The diameter being the outside diameter and the circumference being the inside circumference. Perhaps.
Perhaps as this was a known issue, π = 3 was considered an acceptable standard for illustrative purposes.
The law of the Lord is perfect,
refreshing the soul.
The statutes of the Lord are trustworthy,
making wise the simple.
Psalm 19:7 NIV
It is the glory of God to conceal a matter;
to search out a matter is the glory of kings.
Proverbs 25:2 NIV