At mega corp, I heard HR use the same line about who is "retiring" and who is quitting. "He said he was retiring but he is only 53, so therefore he is just quitting and making it sound better".
Being a huge corporation, they had to set limits / lines /policies about who gets things like retirement parties, extra days off for funeral services, and even who gets flowers and when.
It is about semantics and red tape.
I realized that the specific term "retirement" that has a specific definition to HR, and triggers different paperwork than people that quit -- ie., that you will be receiving your retirement pension benefits. In fact, the term is divided according to "early retirement" before the Normal Retirement Age (with partial benefits), and "Retirement" with full pension.
Normal retirement age = if you retire when your age plus years of service equal 80 (or 90, depending on the retirement plan).
So, you could retire at age 48 with 32 years of service (those people did exist, it was a retail chain), or retire at age 58 with 22 years of service.