Whether you have senior in your title is just nomenclature at pharma companies. Plenty do have it in your title just after PhD, reserving Scientist roles for those coming out of BS who are doing grunt work. That said, other companies have those as “technician” and PhD (maybe masters) is start of Scientist.
Getting hung up on title in Pharma is not a good move. It isn’t uniform at all.
I agree that nomenclature is just jargon. There's also the context of the parent, that senior jobs are typically available right out of university. I do not know the field the parent is in, though. In my experience of the biomedical field, this isn't the case. I'm a postdoc at a good medical school in the US, and most of the postdocs I've interacted with would happily take an industry job if they could manage it - there just aren't enough jobs to go around. The prospects for fresh Phds are even more grim.
Getting hung up on title in Pharma is not a good move. It isn’t uniform at all.