Lowest sizeof(signed char) bits of an object pointer determine truth? No.

ifObjectImplicitCast.m

#if !__has_feature(objc_arc)
#define __unsafe_unretained
#define __bridge
#endif

int main(int argc, const char * argv[])
{
    
    @autoreleasepool {
        
        int true_bits = 0;
        int true_object_bits = 0;
        int ptr_bits = 8 * sizeof(uintptr_t);
        uintptr_t val = 1;
        
        for( int bit = 0; bit < ptr_bits; bit++ ){
            
            if( val ){
                true_bits++;
            }
            
            __unsafe_unretained id obj = (__bridge id)(void *)val;
            if( obj ){
                true_object_bits++;
            }
            
            val <<= 1LL;
        }
        
        // Both true
        NSLog(@"%d %d", true_bits == ptr_bits, true_object_bits == ptr_bits);
        
    }
    return 0;
}