lvl 100, 0 agi... sorry i'm wind i love winds. all my mains are winds. and i have to say its not true. you will get 200+at most with 0agi. so if your friend happen to have a spd ring or kill clive then yes you can reach 400spd. i think they are lying about "no equipment" cause most people don't count specials as equiptment. also if your friend happen have max potentials then and think of that has having "0" spd then they are lying aswell. (plus it will only reach 300 spd)
Now then if they were 100RB then yes you get 400spd. we get like 200+spd every 100 lvl. and 100+spd every 50 agi.
so ask them for a screen shot if someone doens't want to give you proof they can only be left eating their own words.
EDIT; i saw you mentioned them being a wit. so then yes its true. like i said every 100lvl we get 200+ spd.