Nice lighting

Tell Roy that I would prefer to keep the edge of the road,
as I like the white patch of light contrasting with the dark sky.

Just a serendipity snap as I was walking along.

Fair enough, but he'll tell you that because the white patch is at the edge it leads the eye away from the main subject (the blossom) and out of the picture. Likewise the cars.

Not at all. The white patch nicely balances the blossom on the other side,
the main focus being the threatening grey sky over the street.

But according to Roy, if the eye is drawn upwards towards the sky, it's bad.

Light areas catch the eye and draw the eye towards them, whatever the main focus of the picture is meant to be, and for that reason vignetting is used deliberately to keep the eye within the frame.

It's not bad for the eye to be drawn upwards to the sky if that's where the focus of interest is.

Why must you have rules for everything?

1. My focus of interest would be the blossom, which the title suggests it should be.
2. As we've discussed, such "rules" (like natural "laws") are not strictures; they are descriptions of what happens naturally, including what the human eye does when confronted with a particular composition and how the brain perceives what the eye sees. In that surely they're useful. And they're not "my" rules; Roy in fact is the first to apply them to MY pictures.

Roy doesn't apply any rules to your pictures. He just goes by what looks nice.