For starters, 6 of those 18 are fosters it says in the article. Foster cats (normally a mum and kittens) have to be kept in a separate room until the kittens are old enough to be homed. This would be the same wherever the foster home was. The only alternative would be a pen in a homing centre. Also, by definition, foster cats are temporary residents. A hoarder is not someone that has temporary residents that are then rehomed. It's a mental condition (and I have certainly met plenty of cat and other types of hoarders) and I can see no evidence at all that that label applies to this lady.
That leaves 12 cats in a large-ish house with garden. That really isn't that many. I could talk at length about mine (as I've said I have double that number - both of permanents and fosters) and they are all showing every indication of being happy. I don't understand the 'space to hide away' comment. Apart from when there are fireworks, when all my scaredy ones hide in the cupboard under the stairs), I've never seen any of mine hiding. If they get spooked by a builder or something then they're straight out of the cat flap until the perceived danger is gone. And as for 'has she got insurance'. There is no suggestion in the article that the cats aren't well cared for. We have no idea what her finances are - not everyone lives hand to mouth - it would appear that's not a problem.
And I would bet anything that the cats she has taken aren't those that could have easily got homed elsewhere. Just as my permanents have next to no chance of ever having being homed I imagine hers are the same which is why she has taken pity on them. It's what happens when you work in rescues.
Rehoming centres are always full with a long waiting list. If she hadn't taken these then that would be more cats that aren't being helped at all, because there are far, far too many cats for the numbers of homes available.
It would be amazing if people routinely neutered their cats, and we could reduce the numbers of excess cats and all cats could find perfect, loving homes. But we are so far from that situation that it might as well be science fiction and so, in the real world, we need all the homes we can get. Of course rescues have to turn down a large number of homes for a variety of reasons. But there being 12 permanent cats in a large house, which are all well cared for, isn't by any stretch a good enough reason.