To my knowledge, no one other than the officers and the investigators has seen the actual knife in question. So, the only source for the “spring-assisted” point seems to be the arrest report, which said both that it was spring-assisted and a switchblade. Given that it was apparently not a switchblade, I question the accuracy of that arrest report; but, since no one has seen the actual knife, and no information about the actual knife has been publicly released, it’s impossible to say one way or the other.
Notice that his name is misspelled on the arrest report?