Yep - sometimes they can't actually be rotated. It's just marketing, as they technically can but it's not as convenient as the more expensive ones. Or they have included the tether so it passes crash testing, but they don't expect you to actually use it. That kind of thing isn't common in the UK, but is in some other countries where things like legal standards are seen as annoyances to get round, rather than important safeguards!
It all depends on how the tether is situated. The Maxi Cosi ones for example can rotate just fine with the tether attached because it comes around the back of the seat when it's rear facing so it just goes slack when you're rotating and then comes back to correct tension when the seat is clicked into place for driving.
What is your budget and country? I can try to find something suitable for you. I am going to make a wild guess from the picture and say you may be somewhere that car seats are either only recently being enforced or fairly uncommonly used and so perhaps there isn't a huge selection of the bigger brands? Just so many red flags in the picture making me think the company making (or marketing) that seat are not especially invested in their customers using it correctly. You often see this in countries where car seat usage is a more recent thing or a low priority, or the legal "standards" attitude I mentioned above. In this kind of situation you will frequently encounter incorrect information about how seats can be used as well so it can be useful to look for foreign brands from countries where car seats have been established for a longer time and consumers trust in the legal standards. In some countries you have a choice of car seats approved to various different international standards, so it might be for example that you can legally use an American car seat and they might be cheaper. You may also wish to import for example a Swedish seat which can be purchased online and sent to most countries, as they are the gold standard for rear facing seats.
It would also help if you can say what's important to you in a seat. If your DS is outgrowing the baby seat at 11 months he may be big for his age - do you know if he is/what he weighs? If so a standard seat where the harness is no longer used at 18kg might not be big enough to last him very long. Do you want to be 100% certain you won't need another seat until high back booster (I agree to avoid seats with HBB built in for now, as these are often poor quality), or are you happy to take a gamble and see if you need a larger harnessed seat later on? It's likely HBB seats will be more expensive where you are than the UK, but they still tend to be significantly cheaper than harnessed seats (IME, about a quarter of the price in most places).
Do you want to stay rear facing for now? I would strongly recommend it because it is quite dangerous for a child around a year old to be involved in a crash in a forward facing seat. But if you're wanting to forward face, I would rather you pick a good seat to do it in if that makes sense. And when seats are expensive sometimes it's a choice between a decent seat and a very poor quality one rather than it being a choice between rear and forward facing.
Do you want/need an isofix seat or are you happy with seatbelt fitted if other things like convenience, safety and price are right?
It sounds like spin function is a nice to have rather than a definite need, but perhaps you need something which is easily accessible? Do you do long trips and/or does your DS sleep in the car, or would you be OK with something without much of a recline?