What is the Crest Factor?

Crest Factor is defined as Peak divided by RMS. The result is unitless.

Why is Spectre's measurement different than other applications and meters?

Some applications will convert the Crest Factor to dB. Again, this value is unitless, so it's completely unnecessary to do so.

Why do the ballistics settings not appear to do anything?

Ballistics in the Crest Factor value would be non-standard at best since the values are unitless.

There'd have to be a special meter for the Crest Factor since the values aren't exactly in a standard range.