And no, it did not come from a “post-modern” scholar but from St. Jerome:
“He wrote two letters, which are called general, the second of which, on account of its difference from the first in style, is considered by many not to be by him” (De vir. ill. 1; see Ep. Hedib. 120 Quaest. 11).
There are plenty of reasons not to accept 2 Peter as authentic to a pre-68 authorship. The archaeological evidence of both text and tradition display a letter written in the early to mid-second century. Both Origen and Eusebius expressed doubts as to the authorship and these were long before the days of German critical scholars.
See more here but it does not mean I endorse all of the statements found therein.