Correct, time_t second is already in practice not an "SI second" the later being defined by the "counts" in the "atomic" clocks:
"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom" (at a temperature of 0 K)" https://en.wikipedia.org/wiki/Second
That SI second is what I refer to when I mention an "atomic clock second."
The time_t second is effectively simply one 86400th of a day.
"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom" (at a temperature of 0 K)" https://en.wikipedia.org/wiki/Second
That SI second is what I refer to when I mention an "atomic clock second."
The time_t second is effectively simply one 86400th of a day.