Unfortunately, I don't think this is useful in runs. However I find this thing interesting.
The opposite of this sometimes happens to me. That Portals on angled surfaces are displayed without an angle, making it look glitchy. That happens sometimes when I reload a save. I'm just gonna assume, that this is basically the same thing, so I can tell you that it is not useful, cause as you enter the portal it will fix itself and be displayed properly again. It's purely a visual glitch.
An update has been released for SST that adds the command sst_portal_resetisg. This command removes Item Save Glitch and is to be used in place of restarting the game. This is a temporary solution while a more robust and legitimate one is developed.
The reasoning for allowing this is to make the ne