I gentle parent (but don't tend to call it that because of the stereotypes on this thread) and it's definitely not new but as many have pointed out, the majority of people I hear say they do it are actually permissive parenting.
Gentle parents have firm boundaries around behaviour (e.g. not letting a child draw on the wall) but do not believe in punishing them for expressing their emotions. Gentle parenting focuses on helping them acknowledge and label their feelings while maintaining firm and predictable boundaries. It also involves setting them up for success where possible by trying not to expect more than what is developmentally normal.
E.g. imagine you need to go to the toy shop to get another child's birthday present, and you need to bring your toddler with you. We all know that a two year old will want a toy and will likely have a tantrum about it.
A permissive parent may initially say no, but will give the child the toy when they cry because they don't want them to be sad. In this way, the permissive parent is doing exactly the opposite of gentle parenting - giving them the toy to 'fix' an emotion, teaching the child that negative emotions are scary and should be avoided at all costs.
A gentle parent who really is gentle parenting will try and set them up for success. They'll make the trip after sleep/food when the child is in a good mood. They'll explain in advance what they're doing and why. They won't dilly dally in the shop longer than necessary.
If their toddler cries because they aren't getting a toy, they will respond with empathy e.g. "I know you really want a new toy but today we're getting Frank a birthday present." They'll know that it's developmentally normal for a two year old to cry and they'll simply finish up quickly and take them home. They will not buy them a toy.
There's a lot of parents, however, who instead will bundle their child into the car without bothering to think about how it's probably going to go, because the child just needs to learn that they can't get everything they want. They will drive down to the shop, ask the child to help pick the toy for the other child (something a 2 year old is going to struggle to do developmentally as they are only just learning the concept of sharing, never mind something as complex as buying a toy in a shop for another child who isn't there). Then when the toddler cries, the parent will punish them for it, calling them spoilt, telling them to stop crying or threatening that something will be taken away or they won't get any fish fingers or whatever.
My own mum was a good mum but cannot get her head around gentle parenting. When DS cries because he wants his dinosaur pyjamas instead of his digger ones, she will often say "oh how awful for you, it's so terrible" in a mocking voice. This is where we differ. I believe it's genuinely upsetting for him, because he's not experienced many upsetting things before in his life and I don't think he's being naughty when he's crying. I don't change his pyjamas but I explain that the others are in the wash so today we're wearing diggers. I give him a hug, help him identify his feeling and reassure him.
I believe the path to resilience is teaching him to understand his feelings and that they pass and I'm here for him. My mum cannot get on board with validating feelings that she feels are silly and thinks that children need to be taught what is acceptable to cry about and what's not a big deal.
I think it's fine for people to disagree with gentle parenting as a philosophy, but when they say things like "you're not allowed to say no" they're talking about permissive parenting.
What you're describing OP sounds like something else entirely. Not being allowed in the garden or to draw seems extreme and overly anxious. I actually just looked back at the ages and I'm even more confused.. I'm not sure the name for the type of parenting where children aren't allowed to go outside or draw, but us gentle parents don't want to claim them thanks.