(I'm going to call them Xs because referring to them as saint's crosses or whatever can be confusing)

because if it were symmetrical, the white X would look like it's merely a border to the red, which is not supposed to be the case because it's a separate symbol.

there's also optical alignment at play. i didn't find much about this online but as a designer I've learned that diagonal lines, if broken by another object, can look weirdly crooked if perfectly aligned, so if you actually slightly misalign them you can make them look more straight. the red X here is broken, but it still looks centered rather than to the side of the white X.

They did this to themselves.

Because of the way it is! Duh!

To illustrate the equal partnership between England and Scotland. England gets the foreground, while Scotland gets the pride of place in top left corner.

It's because the part representing Scotland is elevated in heraldry over Northern Ireland.

That just means you need to put the kettle on, which as a Brit you will already be doing anyway.

Literally thought it was rotationally symmetrical until I saw this post

You have to house a fighting-age male immigrant in your shed.

Straight to jail

When I worked at a historic site that flew the Union Flag, you had to run around the parade square three times if you screwed up while raising or lowering it. That included hanging it upside down or letting it hit the ground.

You get hanged the wrong way around

If it's been flown at all it's a sign of distress. It's something only racists do, to try and prove they're better then everyone else.

Believe it or not, straight to jail.

According to https://www.flaginstitute.org/pdfs/Flying_Flags_in_the_United_Kingdom.pdf:

Union Flag - If hung horizontally or vertically, the broad white diagonal should be uppermost in the top-left corner.

Did you read the post, sir?