What doesn't seem reasonable is the truncation behaviour. When the output isn't piped, it gets truncated to the width of my terminal. When the output is piped, it gets truncated to 80 columns. I'd expect no truncation when the output is not a terminal.
This is an outdated systemd though (I installed it on a Rasberry Pi [Raspbian] in order to play with it), so this may have changed.
This might be less being smart and getting out of the way. From http://en.wikipedia.org/wiki/Less_%28Unix%29#Usage:
>By default, less displays the contents of the file to the standard output (one screen at a time). If the file name argument is omitted, it displays the contents from standard input (usually the output of another command through a pipe). If the output is redirected to anything other than a terminal, for example a pipe to another command, less behaves like cat.
Of course, the recommended thing to do is use a different program for scripts/pipelines rather than yum, so now there are two different interfaces that need to be remembered. yum looks like a terminal-friendly program, but actually isn't.
journalctl | cat
journalctl truncates at the width of my terminal or at 80 columns if the output is not to a terminal.