I wouldnt necessarially call it a rejection, but it's not an interview invite either. The wording suggests that they interview 6 times what they need to fill their class and keep people placed on hold in a state of limbo just in case those 600 interviewees dont fill out the class.
I got the same thing from them last week. I translate a pre-interview hold as "We are currently preparing you rejection letter, please buy a bunch of preparatory alcohol to wash away your rejection pains. Thanks for the $90 check, sucker."