Eu apreciaria se alguém pudesse me ajudar com isso (e explicar o que está acontecendo

Isso funciona

>>> from numpy import array
>>> a = array((2, 1))
>>> b = array((3, 3))
>>> l = [a, b]
>>> a in l
True

Mas isso não acontece:

>>> c = array((2, 1))
>>> c in l
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

O comportamento que eu gostaria de replicar é:

>>> x = (2, 1)
>>> y = (3, 3)
>>> l2 = [x, y]
>>> z = (2, 1)
>>> z in l2
True

Observe que o que acima também funciona com objetos mutáveis:

>>> x = [2, 1]
>>> y = [3, 3]
>>> l2 = [x, y]
>>> z = [2, 1]
>>> z in l2
True

Claro, sabendo que:

>>> (a < b).all()
True

Tentei (e falhei):

>>> (c in l).all()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()