I'm not sure where you got that impression that 5s were ever going to be removed. The only thing that has been altered was the removal of a bug where having multiple quests for the same fish sometimes caused a number reduction.
A 5 request comes from your abandoning a quest for that fish type earlier, and that abandoned quest had wanted 10 of the same fish type.
IF you've not abandoned any quest, then it may be a bug (and you should report it).