Even with 3.6 I get a different result:

```
Python 3.6.13 (tags/v3.6.13:aa73e1722e, Mar 23 2021, 15:45:49) 
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> help(open('/dev/zero').writelines)
Help on built-in function writelines:

writelines(lines, /) method of _io.TextIOWrapper instance

```

This appears to be because TextIOWrapper.writelines just didn't have a docstring in 3.6.  I can't explain why `help` just gave you the repr of the method, though.