I guess this is a matter of preference. I see when I click a link on stack.lol that the page header remains visible, but the rest of the page disappears (blanks to white) for a second before the next page appears.

I prefer a seamless experience of seeing the next page immediately without a "white flash" first. For instance, if I am looking at a GitHub project page and I click the "Issues" button, in a fraction of a second the page changes to the Issues page without any intermediate disappearance or partial page load.

In most cases, I find transition effects like fading, sliding, etc. to be an annoyance that adds unnecessary delay and visual distraction.