It doesn't make any sense to me why people label Gen Z as 1997-2012, which is only 15 years.

This is the way I see it from Boomer to Millennial:

Boomers: 1945-1957 (12 years)

Boomer/Gen X cusp: 1958-1964 (6 years)

Gen X: 1965-1976 (11 years)

Gen X/Millennial cusp: 1977-1984 (7 years)

Millennial: 1985-1996 (11 years)

It seems like each Core Generation is either 11-12 years, followed by a 6-7 year Cusp before the next Core.

Following that pattern:

Zillennials: 1997-2003 (6 years)

Gen-Z: 2004-2016 (12 years)

Yet, most people view Gen Z starting in 1997 and ending in 2012. If non-cuspy Gen X (1965) starts around 20 years after non-cuspy Boomer (1945), and non-cuspy Millennial (1985) starts around 20 years after non-cuspy Gen X, then why would Gen Z start only 12 years after Millennial? Wouldn't we follow the pattern and start it 20 years later, making it somewhere in the mid-2000s, for example 2004?