I do agree with the majority of what you're saying.
I just don't get the impression that he has any drive to be independent. He doesn't want to apply himself to his studies, doesn't have hobbies, doesn't work or contribute around the house.
He's happy to hold his hand out for money, phone credit etc though. Going out with your mates doesn't make you independent when mummy is paying for it.
And let's not forget the point of the thread, he's made a horrendous false accusation about his mum to retaliate when he didn't get his own way.
With the phone - I wouldn't agree with restricting it as a general punishment - but if his mum has cause to believe that being up on it until the early hours is having a direct impact on his education, restricting it late at night seems like a reasonable response. To me, anyway. As you say, every kid is different.
My parents took a similar 'hands off' approach to yours, I think. We didn't do grounding, or performative punishments etc. They were clear with their expectations though: Act like a child, we'll treat you like a child. Act like a young adult and you can pretty much come and go as you please.
I got myself a double paper round that earned me 56 Euro a week from the age of 14 (1998, so decent money!), my grades were good...I misbehaved a fair bit at school, but if I ever got busted for anything serious, my parents would hear it from me first. I had a list of chores, if it wasn't all ticked off by Friday 6pm, there was no allowance that week. It taught me that you get out of life what you put in.
OPs kid doesn't seem to want to put in, and at nearly 18, I'm not sure what else she can do but turn off the taps on the privileges she's providing. Turfing him out at 18 is an extreme choice...it might be the shock he needs, or it could wreck their relationship.