I noticed similar.
You assign a filament to the model and slice it.
Studio honours the selection and shows the right filament.
But, and that’s a BIG but: When you send the file to the printer there are again selection boxes for the filament to use.
And these only seem to work in order from left to right for the AMS slots.
Means, that if you have similar filaments with the same colour icon the job will always go for the FIRST available filament but not the other if you selected it and it happens to be further to the right in the AMS.
The problem also seems to work hand in hand with the auto resume option to switch to a spare roll when the first ran empty.
I had quite a few prints resuming on the wrong roll.
Wasn’t a big drama as it was the same filament and colour but still.
I think Studio is doing it correctly and that the mess starts with the sending part of the job.