Wrong. At 13A, the rotor is stalled, or damned near (RPM *way* less than unloaded). In addition, you assume 100% efficiency, which universal motors certainly don't enjoy. That's how Crapsman used to rate their tools (still do, sorta).
At *very* high RPM. Different motors and still not 100% efficient. Universal motors are cheap and light. Not much else can be said for them.