"I know of other men who drink a lot more than my partner does now but they're not considered'alcoholics'"
They should be, because that's what they are. But to an extent it's acceptable within society to be a functional alcoholic. Which is not the same thing as saying that it causes no harm.
"He doesn't drink to get drunk"
So he's drinking to alleviate withdrawal symptoms then, he's drinking just so he can feel normal, because without it he's in withdrawal and feeling shit.
"If he starts to feel drunk he will switch to lemonade".
Oh wait, so even though withdrawal has eased he's still drinking. He doesn't stop when symptoms ease, he stops when he starts to feel drunk/tipsy. That's drinking to be drunk. Mildly drunk, but drunk all the same. It's deliberate.
You seem defensive OP. I agree it's hard to be in a society where there's almost an expectation that people will drink, at least occasionally. A society where sometimes, depending on who you're surrounded by, it almost seems unacceptable to be permanently sober. How messed up is that? But it's a choice to ditch people who pressure us into unhelpful unhealthy things, to stand our ground against them if necessary and choose to have people around us who are more in line with our own values. But he values drinking, that's the problem, so he's not going to do that.
There's a difference between your relationship with alcohol and his. Yours isn't going to harm anyone. His will. Already has. Damaged his liver. Oh it's not permanent so that's ok. Really? Really really? Trigger warning The cuts on a self-harmers arm will heal if they're not too deep, so we should just leave them to it, it's not a problem, it's how they cope?
His alcoholism has damaged you too. You're already taking on a higher mental load, feeling responsible for his health, for fixing it or maintaing it. Feeling sad about it, posting on here because you're thinking about it, spending time and energy defending his choices to us. We don't care. We don't know him, we're not emotionally involved. But we care about you, the anonymous stranger on the internet who reached out for help, that's why we're posting. We're not the enemy. Alcohol is, for some people, like your partner. Like you too, if you're not careful. If the earth orbits the sun and the moon orbits the earth, then the moon by default is also orbiting the sun without even trying. Take care.