attr'd classes don't have default attributes?

Today I stumbled over this one:

from attrs import define,field
from dataclasses import dataclass

@define
class N1:
    foo:int|None = field(default=None)
class N2:
    foo:int|None = None
    def __init__(self, foo):
        self.foo = 123
@dataclass
class N3:
    foo:int|None = None

n3 = N3(foo=123)
del n3.foo
assert n3.foo is None

n2 = N2(foo=123)
del n2.foo
assert n2.foo is None

n1 = N1(foo=123)
del n1.foo
n1.foo  # AttributeError

This is not what I'd expect when I decide to attrs-ize an existing class. Thus please either fix this, or add a reasonably prominent section that documents this (and other possible pitfalls) to the manual.

Start by running the issue's @define, field, and deletion example to reproduce the AttributeError, then inspect how attrs handles defaults after an instance attribute is deleted. Compare the behavior with the dataclass and hand-written class examples. Done means either the default is restored as expected or the manual prominently documents this pitfall and related migration concerns.