Inconsistent resize behavior w.r.t. pygame.SCALED

main.py

from __future__ import annotations
from typing import Final, NoReturn
import dataclasses, logging, sys
import pygame
from pygame import Surface

logging.basicConfig(level=logging.DEBUG)

DEFAULT_WIDTH: Final = 1280
DEFAULT_HEIGHT: Final = 720

@dataclasses.dataclass
class GraphicsConfig:
    screen_width: int
    screen_height: int
    fullscreen: bool
    vsync: bool
    fps_limit: int

@dataclasses.dataclass
class AppState:
    graphics_config: GraphicsConfig
    pending_exit_code: int | None = None
    screen_surface: Surface | None = None
    request_tick: bool = False
    request_draw: bool = False

def mainloop(app_state: AppState) -> None:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            # do exit stuff
            app_state.pending_exit_code = 0
        elif event.type == pygame.WINDOWRESIZED:
            gconf = app_state.graphics_config
            gconf.screen_width = event.x
            gconf.screen_height = event.y
            app_state.screen_surface = None

    if app_state.screen_surface is None:
        gconf = app_state.graphics_config  # alias
        app_state.screen_surface = pygame.display.set_mode(
            (gconf.screen_width, gconf.screen_height),
            flags=
                (pygame.FULLSCREEN if gconf.fullscreen else pygame.RESIZABLE) |
                pygame.SCALED,  # XXX here, toggle this
            vsync=gconf.vsync,
        )
        app_state.request_draw=True

    app_state.screen_surface.fill((128, 128, 128, 255))
    pygame.display.flip()

def main() -> NoReturn:
    pygame.init()
    app_state = AppState(
        graphics_config=GraphicsConfig(
            screen_width=DEFAULT_WIDTH,
            screen_height=DEFAULT_HEIGHT,
            fullscreen=False,
            vsync=True,
            fps_limit=60,
        ),
    )
    while app_state.pending_exit_code is None:
        mainloop(app_state)
    sys.exit(app_state.pending_exit_code)

if __name__ == '__main__':
    main()