For the purposes of ICE, the Boolean value True is always the integer value 1, and False is always 0.
But like most (all?) programming languages, any non-zero value corresponds to True, and only zero is False.
Note that negative values are also True; I could stick a Negate node inbetween Get Point ID and Integer to Boolean and get the same set of booleans.
However, in ICE you cannot plug an integer into an If node, so this point is rather moot. In programming, you can do things like “if ( !n )”, where !n evaluates to true if n=0. Or you can do something like “if ( NbPoints )” instead of “if ( NbPoints > 0 )”.