unicodedata.ucd_3_2_0.is_normalized incorrectly rejects NFD with a character unassigned in Unicode 3.2

[augusto-rehfeldt]

Bug report

Bug description:

Documented behaviour: Python unicodedata documentation, unicodedata.is_normalized: "Return whether the Unicode string unistr is in the normal form form." The unicodedata.ucd_3_2_0 entry says: "This is an object that has the same methods as the entire module, but uses the Unicode database version 3.2 instead."

Expected: ucd_3_2_0.is_normalized('NFD', 'A\u0315\u1ab0') returns True.

Actual: Returns False despite the string being NFD under Unicode 3.2.

import unicodedata as ud

u = ud.ucd_3_2_0
m = '\u1ab0'
s = 'A\u0315' + m

if not (u.category(m) == 'Cn' and u.combining(m) == 0
        and ud.combining(m) > 0):
    print('REFUTATION REJECTED: input does not meet the stated premises')
else:
    # These characters are not Hangul syllables. NFD requires no canonical
    # decompositions and nondecreasing combining classes between class-zero boundaries.
    classes = [u.combining(c) for c in s]
    decomps = [u.decomposition(c) for c in s]
    expected = (
        all(not d or d.startswith('<') for d in decomps)
        and all(b == 0 or a <= b for a, b in zip(classes, classes[1:]))
    )
    actual = u.is_normalized('NFD', s)
    if actual != expected:
        print('REFUTATION CONFIRMED:', repr(s), actual, expected)
    else:
        print('REFUTATION REJECTED: actual agrees with independent Unicode 3.2 NFD check')

Output on Python 3.14.6 (Windows-11-10.0.26220-SP0), standard library unicodedata:

REFUTATION CONFIRMED: 'A᪰̕' False True

This report was found and written by an automated property-testing tool I run (bugforge). The reproducer above was executed and its output is pasted unedited; no person reviewed the report before it was filed. The search script is in https://github.com/augusto-rehfeldt/bugforge-results/tree/main/unicodedata-20261003-064954-c1

CPython versions tested on:

3.14

Operating systems tested on:

Windows

[ZeroIntensity]

See #158748 (comment).