Scrum Roles

Isn't this reverting to traditional hierarchical positions ?

It's more likely to be symptomatic of their continuation, and of never having overcome organizational gravity in the first place. Agile change is mostly cultural.

It doesn't necessarily have to be reverting to hierarchical positions, nor is having a hierarchy necessarily a bad thing.

In some organizations, prefixes like "associate" or "junior" or "senior" or "staff" or "principal" refer to experience, which translates into compensation bands. A company may not pay someone who is just entering the Scrum Master role with an entry-level certification (like the PSM I) the same as someone with a decade or more of experience and ongoing continuing education in a variety of frameworks and methods. Having these different titles can help the company categorize people and give clear expectations for what is necessary to progress to the next level.

Sometimes, they may also indicate "individual contributor" (not really the best term, but a common one) versus "management" track positions. An organization may want to denote people with direct reports. If the organization has many Scrum Masters, then it may be useful to have a manager to help each of the Scrum Masters with career development and making sure their contributions to the organization are effective, for both the Scrum Master and the organization.

So, instead of inventing senior position titles by adding prexies,  wouldn't the Agile Coach role work? The Scrum Guide does not provide for prefixes. The different levels of professionalism should suffice-PSM I, II, III instead of reverting to traditional titles. This is my view. 

The Scrum Guide does not provide job titles or job descriptions.  It includes what was previously referred to as roles and now is referred to as responsibilities.   A role does not have to equate to a job description.   For example a role that personnel managers often fulfill is to help the individuals in their organization structure to improve their professional skills.  However there are job titles or descriptions like Program Manager,  Network Manager that would not have that responsibility. Just as there could be job titles like Team Lead, Support Supervisor that would have the personnel manager role.  So roles are related to responsibilities. Job descriptions for job titles contain a list of responsibilities. 

The Scrum framework provides needed responsibilities or roles.  How an organization chooses to assign those responsibilities to their job titles is outside of the framework.

Agree with @Daniel Wilhite

Scrum roles , that defined in scrum guide will be sufficient for a team or a small project.

However for big organizations many scaling framework are present - Safe, Nexus, Less, Scrum of Scrum

For clear roles and responsibilities, one can refer these and align positions accordingly.

For example Safe has defined product manage, ART engineer, SPCT roles, these will help organizations also to scale scrum effectively without juggling with traditional hierachical positions and scrum roles.