The LXX translation does not follow oral Jewish tradition as found in the Jewish Talmud, but the LXX translation is not inaccurate either.
The relevant passage from Philo occurs as follows. Please click to enlarge.
The suggestion is that authority on earth derives its authority from heaven. In this respect, Philo even indicates that parental authority stems from divine authority.
As noted by the reference of the OP, the translation from the LXX indicates "gods" from which Philo appears to have inferred the appellation to include foreign gods and deities in a wider context. The LXX translation however does not seem far from the logic of the Masoretic Text, because the verse juxtaposes the first part of the verse with the second part of the verse through four disjunctive accents. In other words, authority on earth is derived from authority in heaven.
There are four disjunctive accents in the verse. The first is the Tipcha, which continues until the more powerful Atnach appears, which is the second accent. This Atnach is what separates the verse into two logical halves. The Atnach contrasts whatever follows until the verse terminates, when the all-powerful Siluq appears. The third accent is another Tipcha, which, unless another more powerful disjunctive appears, will subsume whatever follows until the end of the verse, which completes the thought of the verse. The Sof Pasuq is the colon mark (:), which functions as the "period" for the Siluq. So the two Tipcha accents appear parallel. The logical suggestion from the cantillation is that authority on earth stems from authority from heaven.
So the "gods" mentioned in the LXX suggest higher authorities. If Philo were familiar with the LXX (and he was), then the term "gods" in Exod 22:28 in the LXX is not a reference not to pagan deities, but to angelic authorities, which are not to be reviled (cf. 2 Peter 2:10 and Jude 1:8) . Please click on the image below to enlarge, which is taken from Philo's commentary On the Creation VII (27).
Philo's interpretation of the LXX version of Exod 22:28 was therefore not in reference to pagan deities, but to angelic power and authority. If this approach was his interpretation, then his application of this verse was not to revile any reference to the appellation of "God" (or "god"), since authority (whether God as the Creator; Gods as angels; or "gods" as deities worshipped by the pagans) stemmed from above, and therefore had merited all reverence from below.
Yonge, C. D. with Philo of Alexandria (1995). The Works of Philo: Complete and Unabridged. Peabody, MA: Hendrickson, 509.