That shouldn't be the case?

When a negative leap second is applied it just means that 23:59:59 is skipped. The seconds go 56 57 58 0 1 2 3.

vs a positive leap second where time goes 56 57 58 59 60 0 1 2 3.

So if you are billed by time and it's tracked via a timer then your time is still accurate but if it's tracked by reading your start and end time then your billing will just read an extra second.

Positive leap seconds are harder as they require you to reason about a clock that includes a 60th second but systems view negative leap seconds as if nothing happened for an entire second.

Now there are some cases where this runs into issues. If you have jobs that fire off based on the time then you can get jobs running a second early. Normally this shouldn't be a problem but in some cases this could result in contention of resources.

You could also accidentally trigger watchdogs but any watchdog worth its salt will use a real timer not wall time.

But overall negative leap seconds are way easier as they are still monotonically increasing and don't require downstream systems even understanding the concept of a leap second in the first place.