Seventy-one of the seventy-two are paired with verses from the Psalms. The seventieth is paired with Genesis 1:1, the first sentence of the Hebrew Bible.
The exception is not hidden and is not disputed; it appears in the standard lists. What it does is expose the apparatus.
If the verse pairings followed a stated rule of letter-correspondence within the Psalms, an entry pointing outside the Psalter breaks it. Either the rule was never restricted to the Psalms, in which case the near-uniformity of the other seventy-one needs explaining; or the rule admits exceptions, in which case it is not doing the work it is credited with; or this pairing was made on other grounds entirely.
The most likely reading is the third, and the grounds are visible. The seventieth angel is associated in the tradition with generation, regeneration and rebirth. Genesis 1:1 is the verse of creation. The pairing is thematic. Whoever made it was matching sense rather than letters.
That single exception is worth more than a great deal of general argument about the verse column. It shows a compiler making a judgement, and it shows that the apparatus was assembled by people exercising judgement rather than generated by a procedure.
Which is exactly what the provenance of the verse column independently suggests: it is late, it is Christian in its numbering, it is not present in the medieval Jewish sources that describe the derivation, and it reaches modern lists through the tabulations of the nineteenth century. A rule is asserted for it. An exception sits in plain sight in every printing. Both facts are usually reproduced together without either being noticed.