cmake_policy(SET CMP0077 NEW) not working correctly ?

Use case : including the poco libraries via FetchContent into my build tree. And I want the poco libraries to be build in a static way. The policy does not work and keeps giving warnings, I can only make it to work via : set(POCO_STATIC ON CACHE BOOL "").

I stripped the setup down to the following to reproduce :

MYDIR
|
+ CMakeLists.txt (1)
|
+ poco
   |
   + CMakeLists.txt (2)

The content of (1) :

cmake_minimum_required(VERSION 3.15 FATAL_ERROR)

project(dummy)

cmake_policy(SET CMP0077 NEW)  # this does not seem to help at all ????
#set(POCO_STATIC ON CACHE BOOL "")
set(POCO_STATIC ON)

add_subdirectory(poco)

and the content of (2) :

cmake_minimum_required(VERSION 3.2.0)

project(Poco)

option(POCO_STATIC
  "Set to OFF|ON (default is OFF) to control build of POCO as STATIC library" OFF)

message(STATUS "${POCO_STATIC}")

When invoking as : cmake -D CMAKE_BUILD_TYPE=Release -H. -Bbuild ==>

CMake Warning (dev) at poco/CMakeLists.txt:5 (option):
  Policy CMP0077 is not set: option() honors normal variables.  Run "cmake
  --help-policy CMP0077" for policy details.  Use the cmake_policy command to
  set the policy and suppress this warning.

  For compatibility with older versions of CMake, option is clearing the
  normal variable 'POCO_STATIC'.
This warning is for project developers.  Use -Wno-dev to suppress it.

-- OFF

So we see we get the warning, and it is still OFF.

According to : https://cmake.org/cmake/help/v3.16/policy/CMP0077.html, it seems it is intended for the use case I want to carry out.

Is this indeed a bug, or am I doing something wrong ?

I can make it work, by setting in (2) the minimum required also to 3.15. But that is the problem, I am not in charge of that CMakeLists.txt, and I shouldn't be, right.