The /setidletimeout n command sets the idle timeout to n minutes for every valid positive integer, but disables the idle timeout when n is 0.

However, in both cases, the following message is displayed:

The player idle timeout is now n minute(s)

This message is confusing because a value of 0 is special-cased to disable the idle timeout. I would expect the message to instead indicate the idle timeout has been disabled (and potentially also use a different command in general, e.g. /setidletimeout off?)

The value 0 also differs from the special case for max-tick-time which is instead -1, which is more obviously a special case.