At 150% scaling, one logical pixel maps to 1.5 physical pixels. When a 1px grid line is drawn, the renderer cannot light exactly 1.5 pixels, so it distributes the color across adjacent pixels using anti-aliasing. Depending on where the line falls relative to device-pixel boundaries, one pixel may be fully colored and the next partially colored, or vice versa. This shifts the perceived center of the line slightly. In a repeating grid, these fractional shifts accumulate, making the gaps between lines appear uneven or "vibrating."

Chromium often avoids this by rendering 1px borders as hairlines that snap to a single device pixel, even when a CSS pixel corresponds to 1.5 device pixels at 150% scaling. This keeps lines crisp, but it also means the border remains about one device pixel thick, making it appear slightly thinner relative to the surrounding content.

For some people such artifacts are not noticeable for others they are.

Here are some links that explain the issue:

https://patrickbrosset.com/articles/2024-06-21-invasion-of-t...

https://flutterawesome.com/sharp-looking-flutter-application...

https://tanalin.com/en/articles/integer-scaling/