Does the "realism" entail significantly more complex processes to diagnose and treat diseases and more logistics and budgeting to keep the hospital afloat or does it just mean instead of funny fictional diseases I get some mumbo jumbo about hepatic cells and bacteria with weird latin names? Because while the former definitely interests me the latter alone doesn't mean particularly much.
Yes. There are over 200 different diseases/illnesses and they are all made up of different symptoms (between 2 and 10 symptoms per illness that I have seen so far, also a ton of different symptoms) and there are literally dozens of different tests. Just the GPs office alone can run about 6 tests and if you have a STAT lab you can run about a dozen. Add in MRIs, CAT scans, X rays etc it gets a lot more complex. A cool thing about this is that you can also diagnose and treat patients yourself (by choosing what tests you give or treatments you give) so it can be much more involved if you want to do that.
When it comes to emergencies they are also handled in a much more "fun" way (in my mind). In TH Emergencies were simply a large amount of people with X illness walking in at once which essentially tested your capacity and maybe your doctors speed. In this game when there is an emergency (either from ambulances or from a patient collapsing in your hospital) they will be taken to the trauma department and then you have to diagnose and treat them as quick as you can; I find the player control system of treating them yourself makes this 100x better because its actually thrilling and when you fail or succeed its a lot more impactful. After the trauma room where they are stabilized you can put them in an ICU room and do more tests, send them to surgery, send them to another hospital if you can't or don't want to treat them etc. Unlike in TH, finding the real issue may be a lot more difficult in some cases...the emergencies are usually just stuff like "got in a car crash" and they may have a broken bone or they could have full on internal bleeding...but you won't know until you run the right tests (having a good doctor helps as interns and lower grade doctors can misdiagnose them or completely miss a symptom and make it much worse).
Budgeting and balancing your expenses is also a lot more involved than TH. One of my biggest issues with TH was that you could just plop a handful of rooms. Get yourself a nice profit margin...and....that's it. No real challenge once you learned the right "formula". This game has been much harder to find the "formula" to just make it work with no challenge. You also get your patients from different insurance companies so you more or less can filter and choose what types of patients you might get if you want to which can play into your budgeting. Employee wages are a big consideration especially at the start.
On a final note, this game also does a wonderful job of balancing micro vs macro management. You can literally place every object like the sims or you can just plop premade rooms (you can also make your own prefab rooms). You can let your doctors handle patients or you can handle them yourself. You can control what types of patients you get (to a degree) which allows you to take as many people and types of issues as you want or you can just run a little clinic and tweak it all day to your hearts content etc.
So long story short, no, it is not just a change of names but rather a much more nuanced system that is a lot more hands on for the player. Where in TH you could plop rooms down and essentially turn the game into a screensaver, that has not been an issue with this game so far.