If you ask me than Bambu went the wrong with the profiles.
Thanks for confirming by json findings by the way!
If I check my now defunct favourite, Simplify3D, or literally any other half decent slicer I find proper profiles.
Bambu however works with a staged control system.
Literally everything is mixed together on a basic level first.
E.g.: Machine configuration, nozzle type and such.
Then the filament settings are mixed in, followed by the actual print settings.
And here the issue already starts for me 
It is next to impossible to create proper filament profiles of the custom kind that Studio leaves untouched.
I use quite variety of plates/films on them, with that comes the need to have matching profiles.
Being unable to define build plate setting in any meaningful way su(ksā¦
But if I enter, for example āShittament PLA dark greenā and fill the profile with my settings I am happy camper.
Until I change any setting for a different Shittament roll - Studio always tries to apply what you change to all custom filaments in the AMS selection.
Quite a bummer if you need different settings for different colours, one mistake and they all end up the same.
Worse still, as you noticed as well, with the print profiles.
As I had to start from generic PLA, it is also the entire base for the custom profile.
Worse still: The internal settings we canāt see or change seem to also depend on the lay height and quality defaults of the profile you start with.
Found that out the hard way when it seemed impossible to calibrate the low ratio for a new filament.
The base profile was the 0.08 high quality one, which I selected because I know the acceleration settings and some other things work fine with my holo plates.
But I needed 0.15mm layersā¦
Nothing worked out no matter which way I tried to get the flow rate and k-factor honed in.
Only after starting from a 0.12mm profile I got 0.15mm working as expected.
Ideally a custom profile should be fully custom and stay that way.
Especially if someone created a profile with model specific needs.
No other printer I ever had made a mess out of things like Bambu does
And doing manual backups of all relevant files whenever something is updated is just becoming too much of a hassle.
So I rather stick with something that works and is properly tested by users confirming it does than to jump onto every update to find out my old files no longer produce acceptable prints.
While I agree that from a viewpoint of just simplification the Bambu approach makes sense:
I am getting the distinct feeling that all this is intentional.
The filament manufacturers Bambu supports come with their own base profiles and all - which seem different in some areas to the Bambu or default ones.
On the other hand profiles a user creates only ever contain what little we can change in Studio but none of the often vital other factors.
For the user this means that once hey established a working filament and print profile it might all go down the drain with the next update.
No clue why but if a default profile changes a custom profile that had THAT setting unchanged has the updated setting applied.
Imagine, as a worst case, that ācombine infillā would change in the default.
That unexpected change in flow can make a total mess out of a model printed in 0.08mm layersā¦
I mean: What do you eventually do if you need those printer running to pay your bills?
You revert back to filaments that are already fully supported, preferably Bambu ones 