So this is interesting... I did this, and it only shows up in the preview/thumbnail view. Once I click on the thumbnail tile to view the image in full screen, it goes back to flat red with no logo.

Okay, some sort of curse is in play here.

Take a screenshot of the full-screen image. Do you see the logo flash?

Zoom in to the image. Do you see the logo appear, but only near the edges of the display?

Computers!

I'm not getting that - in Photos, looking at the full size flat-red version, and taking a screenshot, I don't see the logo flash at any time during that process. Nor on the edges when I resize.

Augh. Bizarre. Oh, do you have the "pop-up" overlay with icons for share, filters, etc. visible? (The one which appears when you tap the image.)

On my Pixel 3 XL, the behaviors I described occur, and also the logo is invisible unless the overlay is shown (in which case it's drawn only near the edges, unless you're taking a scree...oh.

I get it.

Image math is getting done internally in a wide gamut. Including alpha blending. But it's converted to sRGB before being displayed.

The things I described all, I suspect, modify the image- mostly by just dimming it, and the resulting dimmed wide color values map to different sRGB colors (where the undimmed colors all map to the same shade of red.)

I have a hunch that the internal management of the image by the application you've described is similar to the case of another comment where the logo could be seen in Windows after saving the file in MS Paint.

it's entirely possible that the preview compresses the color space in just the right way to show the separation. reducing colors can shrink image sizes quite a lot.

as to what's actually happening: not a clue! just pointing out possibilities :)