WRT toxoplasmosis - it's actually pretty hard to contract from cats if you wash your hands after the litter box cleaning. You're in fact more likely to get it from eating raw veggies, I believe. Our veterinary assistant was actually incredibly surprised she hadn't had it when she got pregnant and tested for it considering all the 'cleaning' she does. And for non-pregnant people they usually don't even notice that they've contracted it and are fighting it before it leaves their system - which is why they have to test for it to see if a person has had it so...it's usually no biggie
Err and that study doesn't show cats don't care. It's just that cats don't do hierarchy in the same way dogs and people do. Dogs and people are both omnivores that live in packs so they are opportunistic and share a social structure that is familiar - which makes them more comfortable to train to us. Hence, it is easier to command (and abuse that power on) dogs.
Cats however are incredibly in training us
and negotiating their needs - the reason they meow is in fact for our mutual benefit. They learned to use a vocalised language because we're too dense to actually understand body language and are willing to go the extra mile in communicating with us. Normally, their meows don't get used in feline communication, safe from with their kittens. Wrt to forming intimate bonds - only few are allowed within their personal bubble for cuddles, and their owner is usually one of em for a reason.
The thing is that they don't do hierarchy in the strictest sense - each individual is on their own and negotiates their own troubles in life. Nobody has authority over you - but you can negotiate with others to navigate common resources and certain perks to better your life. The only actual exchange of services they seem to do is care of kittens - you watch mine while I hunt and vice versa. Other than that, they're on their own in life.
So calling their name, unless properly taught that there is a good reason to come when called (and that is really not that hard to establish) is pointless. There is no pack to answer to. Mine comes though to a specific place, from wherever she is in the neighbourhood when i ring a bell - something I taught her in 3 days - because she knows it means wet food or a treat. I trained her in a hurry before going on holiday so my brother in law could actually medicate her while we were gone as she'd gotten hurt. It's that easy.
My guess is that in that study, their response to their name being called by their owner depended on their relationship and their motivation history with that owner. Cats who are affection or interaction-motivated tend to be the easiest to train to respond to that, unless people consciously use a bribe each time they call- many cats are food-motivated as well. I'm betting a great deal make the mistake of calling their cat to get them inside, which robs them of their freedom and is in essence experienced as a punishment almost, diminishing the effect of the name calling greatly. The same happens when people call their dog to leash them after letting them run free - the dog doesn't exactly feel motivated to listen after a few times anymore.