"grep | head" doesn't limit the length of output lines, but "grep | cut" would.

However, ack and ripgrep's default unpiped output is grouped by file, and if you pipe the output, it doesn't do the grouped output.

The idea of "supposed to be used" is also different for ack than it is for grep. ack is specifically less of a general-use tool than grep. It's meant for searching source code. This is also why I have never said that ack is a replacement for grep.