Unfortunately, something about this change isn't a no-op. It seems more tests are getting picked up (and are thus failing)?

Indeed :-).

This one and its relatives look similar to #28023

__________________ [doctest] numpy.core.numeric.dtype.fields ___________________
EXAMPLE LOCATION UNKNOWN, not showing all tests of that example
??? >>> print(dt.fields)
Expected:
    {'name': (dtype('|S16'), 0), 'grades': (dtype(('float64',(2,))), 16)}
Got:
    {'name': (dtype('<U16'), 0), 'grades': (dtype(('<f8', (2,))), 64)}

Not sure if "Got" valus are "more correct", or it needs a # may vary (endianness, unicode).

This one looks genuine, too:

_________________ [doctest] numpy.lib.introspect.opt_func_info _________________
028     --------
029     Retrieve dispatch information for functions named 'add' or 'sub' and
030     data types 'float64' or 'float32':
031 
032     >>> import numpy as np
033     >>> dict = np.lib.introspect.opt_func_info(
034     ...     func_name="add|abs", signature="float64|complex64"
035     ... )
036     >>> import json
037     >>> print(json.dumps(dict, indent=2))

The whitespace is not a problem, but values do differ. Maybe it needs a # may vary (architecture) or some such.

-          "current": "FMA3__AVX2",
  +      "current": "AVX512F",

IOW, the scipy-doctest change is a noop w.r.t 1.7.1, but numpy was pinning an older version which misses some tests.

Okay, the CI is green now after 425a603. I've to admit I've no idea what the dtype.fields are or should be, just copied the output into the doctests and it did the trick. Happy to apply a different fix if there's one.

Doc changes look right -- clearly not picked up in a long time -- thanks Evgeni!