Sony phones are named like their cameras.

First number is the model (1/5/10); smaller is more premium.

Roman numeral is the generation (i/ii/iii); bigger is newer.

It's about as straightforward as they come when it comes to phone naming. The competition names things <generation number> + Mini/Pro/Pro Max/SE or S/Z/A/M <generation number> e/Lite/+/Ultra/FE or <generation number> +a/a(5G)/Pro/XL.

Wasn't it Canon who does it that way?

IIRC there was a7 and a9 and a9 was better (ignoring the "r" numbers).

On the other hand Canon's 1D is the flagship, next 5D, then 6D, 7D, then things mess up at higher digits where larger number within same digit count is the newer, yet less number of digits is the more pro model.

Yeah, Sony cameras are higher number models are higher positioned models. Canon is lower number is higher positioned models. But they follow a very boring number/variant/generation naming scheme. At least until they announced the a1 which is positioned above the a9.

Then there's Nikon that just decided to pick numbers outta a hat.