That's why I used the scare quotes. "Seconds" are the units the computer stores, but 7 months later nobody cares how many seconds have passed. They care how many months, days, hours and minutes have passed.
The SI second is different than the second that most people care about. When people speak of seconds, they're usually speaking in terms of remainders of a minute, which are remainders of an hour, which are remainders of a day. People chunk time, the same way we chunk everything else for our memory.
The day is a fuzzy unit, and equivocating day units with second units is always going to fail. So you can either redefine the day (as industry wants to do by changing UTC), or you can redefine the second, as POSIX effectively does. Or, I suppose, software could stop using second units for storage, and use expanded date-time descriptions.
I say that POSIX time is beautiful because it, rather accidentally, codified a redefinition of the second. And it turns out that it works very well for many use cases, both where you produce output directly for human consumption, or for inputting into algorithms which collaterally produce output for human consumption. It's a manifestation of the worse-is-better principle, where you sacrifice a quality like elapsed second precision for other qualities--simplicity and, depending on the context, robustness. However, it's just horrible for cases that rely on precise SI seconds, and it's clearly not simplistic from the perspective of the kernel.