Sony model names follow a simple scheme – the letter indicates the year. For example, “H” was used for 2018 phones.
The User Agent profiles for three Sony units were discovered J8110, J8170 and J9110 . The “I” generation wasn’t skipped over, there are UA profiles for the likes of I4113 and I4312.
So, we wouldn’t have expected to see J-phones until 2020. Look at that resolution, 1,440 x 2,880px. That’s a pure 18:9 or slightly taller as UA profiles don’t always include things line on-screen buttons in the reported resolution.
The screen is not nearly as tall as the 21:9 Cinemawide panels for the Xperia X24. And this is very definitely a flagship device.
The first digit in the model name denotes device class and SIM count – 8 is flagship, 9 is dual-SIM flagship, 3 is mid-range, 4 is dual-SIM mid-range.
The J9110 is just the dual SIM version of the J8110. The digit is used for different regions/modem versions, so the J8170 should be the same phone again, just for a different market.