LOAD_FAST access names outside of co_varnames

Documentation

LOAD_FAST is documented (https://docs.python.org/3.13/library/dis.html#opcode-LOAD_FAST) as:
Pushes a reference to the local co_varnames[var_num] onto the stack.

However running dis on the following snippet shows that it may load other names:

def simple_cellvar():  # a cellvar in f
    a = 1

    def g():  # a freevar in g
        return a

    return g

import dis

dis.dis(simple_cellvar)
print()
print(f"Var names {simple_cellvar.__code__.co_varnames}")

Output

--           MAKE_CELL                1 (a)

   5           RESUME                   0

   6           LOAD_CONST               1 (1)
               STORE_DEREF              1 (a)

   8           LOAD_FAST                1 (a)      <---- a does not appear in the co_varnames !!!
               BUILD_TUPLE              1
               LOAD_CONST               2 (<code object g at 0x0000027404FB0ED0, ...)
               MAKE_FUNCTION
               SET_FUNCTION_ATTRIBUTE   8 (closure)
               STORE_FAST               0 (g)

  11           LOAD_FAST                0 (g)
               RETURN_VALUE

Disassembly of <code object g at 0x0000027404FB0ED0, ...>:
  --           COPY_FREE_VARS           1

   8           RESUME                   0

   9           LOAD_DEREF               0 (a)
               RETURN_VALUE

Var names ('g',)

Start with the LOAD_FAST entry in the linked Python 3.13 dis documentation and reproduce the supplied simple_cellvar disassembly. Check how the displayed name relates to co_varnames and cell variables, then update the documentation so its description matches the demonstrated behavior.