To me this just seems like a waste of a senior engineer, you could replace the second senior with a mid-level and have the senior lead their own team, which allows the mid-level engineer to grow and reduces head-butting.
Seriously, skills multiply. If two senior people can’t get along and complement each other one or both of them shouldn’t be called “senior.”
It's good to keep in mind that junior/mid/senior are shorthand for a spectrum of abilities, not hard milestones in a career. And where a person sits on that spectrum depends on the project, domain, and team, not on number of years or jobs listed on a resume.
Some more junior programmers bring a lot of talent and enthusiasm to a team, some need more guidance and deliberate mentoring and practice. Some understand the business domain, some don't. A lot of individual personality comes into it. I've worked with juniors who need almost no day-to-day supervision, and I've worked with so-called senior programmers who need their work checked every day lest they go off into the weeds.
The main ability I would look for in a junior programmer is communication, both listening and voicing ideas and opinions, attention to detail, caring about the business domain, and getting along with and cooperating with other team members. If they simply can't learn to write production-quality code that will be evident fairly soon (if they even get through the interviews). It's the people who can write code but can't work with a team or larger organization who drag projects down.
Ability to cooperate should be a hard requirement. History and actual studies have repeatedly demonstrated that individual personalities and team dynamics (mainly around communication and cooperation) are first-order drivers of project success. Any programmer with a few years experience knows that one person on the team can derail the project with conflict, and that is far more damaging than choosing the "wrong" language or framework or tabs vs. spaces. A programmer who can't communicate (both with the team and with management and customers), cooperate, compromise, mentor junior programmers, listen to ideas, and put a plan for success together that leverages individual talents is not "senior" except maybe in years.
Everyone who works as a senior engineer has some strengths and weaknesses, so inevitably you will get some seniors with the weakness that they don’t get along well with other seniors.
People who can't get along in the workplace, or in the rest of life, not only hinder themselves. They can damage a team's productivity and cohesion, and sink a project. Over time I have come to value "people skills" over technical chops, though it's nice to get both, and when I work with someone with good people, communication, and technical skills I think of them as "senior" regardless of their actual age or years of experience.