The specific number ten is tricky because in a healthy environment, the effect tends to dilute. The difference often appears when a team penetrates into the jungle of a new technology. Some people are much better trail blazers than others and in that situation 10x or even higher multipliers are not unusual.

But once the mechanics are known and the pitfalls are spotted, the difference should be much smaller, provided knowledge is properly transmitted through documentation, pairing or whatever.

Actually, a wise boss won't put the 10x programmer to work in parallel with the rest, but some weeks ahead, as a minesweeper.

Edit: another area in which some programmers are much better than others is bug hunting. But again, there's a moment when every evil schrödinger-ish bug is fixed.

If you haven’t seen a niffler you wouldn’t know what people mean either.