odin pc doesn't erase everything?? topic

hey guys i was under the impression that if i flashed stock firmware using the pc version of odin it was supposed to format my phone to clean without having to use recovery to delete everything.
this isn't the case with me, odin pc (ver 1.85) seems to be dirty flashing these stock roms on my phone if i don't wipe in recovery.
is this right or is something wrong here?