Isaac, depends on the mfg.. If they are cheezy (which quite a few are) then they'll include the swimstep in the length of the boat. The boats overall length and the running surface are two different lengths.. Historically speaking those that don't cut corners or misrepresent typically measure running surface.
(Disclaimer, this is primarilly based off the custom boat market, aka performance boats)
Integrated swimsteps (even though they are fiberglass, and part of the boat) should NOT be included in the length of a boat, but about a 50/50 split on who does and who doesn't.