The "or the like" was the end of the list of ways in which you could model the divergence between Unix time and the number of SI seconds between January 1st 1970 UTC and the present.
One way of modelling it is as saying that seconds in Unix time all have the same length, that differs by some factor from SI seconds, though that factor changes every time a leap second is introduced.
Another way is to say that seconds don't all have constant length; some seconds have a different length than the rest of the seconds (like those in the hour or day leading up to a leap second, or even just that the one second before the leap second is twice as long as a regular second).
The "or the like" was just a hedge against other possible ways of describing this divergence that I hadn't described in that one quick sentence.
Pretending that leap seconds don't exist is all well and good if you have a completely closed system, but as soon as you try to synchronize with or compare timestamps with UTC, you'll start running into problems.
One way of modelling it is as saying that seconds in Unix time all have the same length, that differs by some factor from SI seconds, though that factor changes every time a leap second is introduced.
Another way is to say that seconds don't all have constant length; some seconds have a different length than the rest of the seconds (like those in the hour or day leading up to a leap second, or even just that the one second before the leap second is twice as long as a regular second).
The "or the like" was just a hedge against other possible ways of describing this divergence that I hadn't described in that one quick sentence.
Pretending that leap seconds don't exist is all well and good if you have a completely closed system, but as soon as you try to synchronize with or compare timestamps with UTC, you'll start running into problems.