Now that, my friend, is a bug, which happens after you die once - the game should reset your invulnerability to false in case you had one, but it sets it to true instead - I forgot to change it after testing with god mode on... Thanks for discovering it! I'll push a new build soon.
Normally, the sword can only break through boxes and wooden doors. In a situation like in the picture, you just have to jump a bit earlier to manage to slide in time. I will make the slide transition a bit faster as well.