It is an entry level job - it's the lowest tier in their ranking, it's the starting place, it's literally the level where new people enter the organization; it's the lowest paid and least respected position they have, filled with the least experienced and least tenured people in the whole company. It's just that they (want to) start with people who have worked (somewhere else) for a few years already; but that does not and can not make it a mid-tier job, that would require them to have other, even lower jobs.

Furthermore, saying that 3 years might be a senior level position is stretching definitions - assuming an average lifetime career of 30 years, someone with 3 years experience has less "seniority" than 90% of the workforce.