That's not the rule with all antibiotics. Do they still use Penicillin?
The times you've put, fruitsalad, means there's 12 hour gap in your schedule between 6 pm and 6 am. Probably not good. I seem to get quite a lot of these and take them when I first wake up (about 7 am), about 13:00, then about 19:00 then just before going to sleep. I eat about an hour or so after the first three.
I think the reason is that some antibiotics can cause stomach upsets and they don't want you to be sick.