Effectively no. I was wondering too, as /home should be not possible and fail. I asked Timothee about it when testing Kinoite/Silverblue for the first time, and I think to remember that he was not aware of this before as well: /home is done by anaconda that way, but generally it should be /var/home, not /home. However, systemd resolves /home automatically into /var/home, which means it does not “hurt”. However, it is an unnecessary complexity that can cause confusion, and I assume over time, this will be changed. But there is a long way for anaconda to go before the immutables can become default: I just opened a bug report as anaconda keeps crashing with an error when a user by accident mounts something else outside /var, rather than just informing the user that this cannot work. It took me some time to get my error in reasoning that resulted out of old habits (although my notes were correct, I intuitively mounted my main data partition in /<dir> rather than /var/<var>)
The other thing is obviously that anaconda happily creates a / mount in fstab → I might add that to the report to make aware (though I tend to wait for having an evaluation of your case as you indeed have / enabled
). Anyway, we still have time to make anaconda immutable-proof 
The same for me. Though anaconda allows the use of two tools to implement this, and their results are not necessarily identical. Unfortunately, I don’t have time to engage in much testing, comparing, reproducing, etc atm. The other thing is of course that there are further differences in how people customize their partitioning.
Keep in mind that the fstab is stored on root: this means, root needs to be mounted in order to access fstab. Therefore, the dependency you assume would result in a chicken & the egg problem
Effectively, the root mount on boot is done after grub (see the config files of your grub entries). Concerning details of how all things are done to boot an immutable and where differences are, I remain hesitant though, as I am myself new to the immutables.
Off the cuff, the major difference I see is that you have ext4 on your root. However, as long as there are systems that successfully work with that /, I will not add a post about this to the bug reports/feature requests. The existing workaround indicates that the developers know about the general issue anyway.
Just to be sure “explicitly” that we talk of the same thing: when you do systemctl status | grep State, the first line of output is State: running, right?