repro

Disassembly of bar:
 11           0 LOAD_GLOBAL              0 (print)
              2 LOAD_CONST               1 ('bar')
              4 CALL_FUNCTION            1
              6 POP_TOP
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE

Disassembly of delayed:
 18           0 LOAD_GLOBAL              0 (time)
              2 LOAD_METHOD              1 (sleep)
              4 LOAD_CONST               1 (1)
              6 CALL_METHOD              1
              8 POP_TOP

 19          10 LOAD_GLOBAL              2 (func)
             12 CALL_FUNCTION            0
             14 POP_TOP
             16 LOAD_CONST               0 (None)
             18 RETURN_VALUE

Disassembly of foo:
  7           0 LOAD_GLOBAL              0 (print)
              2 LOAD_CONST               1 ('foo')
              4 CALL_FUNCTION            1
              6 POP_TOP
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE

Disassembly of func:
 11           0 LOAD_GLOBAL              0 (print)
              2 LOAD_CONST               1 ('bar')
              4 CALL_FUNCTION            1
              6 POP_TOP
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE

repro.py

import functools
import time
import threading


def foo():
    print('foo')


def bar():
    print('bar')


for func in [foo, bar]:

    @functools.wraps(func)
    def delayed():
        time.sleep(1)
        func()

    t = threading.Thread(target=delayed)
    t.daemon = True
    t.start()

time.sleep(2)
# Output:
# bar
# bar