Why does a humanoid avatar's (in preview mode) pose gets applied whenever I enter play mode and use animator without animation? (default pose)

Hello, the problem I have is that, whenever I use a humanoid avatar, it's pose becomes weird by default (not T form, even though I exported it in T pose). Also, the main problem is that the default avatar preview mode gets applied whenever I enter play mode. If I have animations on, it overwrites the pose, so it's fine, but if I have no animations in animator, or if I use avatar mask and deselect some body parts, those parts get default avatar pose (not the pose from the edit mode). So my question is: how to ignore the avatar preview pose when you start the play mode or how to use edit mode's pose in play mode too?

Note: if I use non humanoid avatar, it works well, but I want masked avatar with some isolated parts, so I would like a humanoid avatar.