AFAICT, these companies don't really promote within a title - they use a leveling system. The definition of a promotion is to move from one level to another.
Vague job titles like "senior" or "junior" can be useful in limited circumstances, but if a company can promote you within the same title, it's a bit of a smell.
Promotions within the same title ... aren't really promotions.
I've worked at companies where titles beyond junior & senior (and "senior" means 3 years experience) don't exist