The bad example has significant lag compared to the good.

Also, except when the pointer is over something, it isn't actually a pointer so you might not be able to position it precisely onto something. While trying to position it over something small⁰ it is going to cover the target making the process partially guesswork.

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[0] ignoring for a moment that something so small is likely bad UX in itself, like the single-pixel¹ border drag targets and scrollbars found on many things these days

[1] see similar discussions over in the thread about older UIs at https://news.ycombinator.com/item?id=48104428 for this and related issues - even when we have far fewer pixels on the screen a single pixel wide/tall/both target was often considered bad form.