Interesting that the LXX renders "the form/similitude" of the Hebrew text--referring to YHWH (Jehovah)with τὴν δόξαν κυρίου . . . (Numbers 12:8)
Moses beheld the "form" or "glory" (LXX) of Jehovah. Compare Ezek. 43:2. However, in Ezekiel, we have כָּבוֹד: while Numbers has תְּמוּנָה.
See Ps. 17:15.
It has been suggested that LXX translators sometimes use morphe and doxa interchangeably. Cf. Job 4:16.
Hanna K. Tervanotko explains that the Septuagint "makes the text easier to understand." She thinks the MT is somewhat vague or unclear as to what Moses witnessed, but the LXX suggests he beheld God's glory. What consequences follow from the LXX rendering? Tervanotko reckons that the Greek version makes it evident Moses "did not see God directly."
See Tervanotko, Denying Her Voice: The Figure of Miriam in Ancient Jewish Literature, Vandenhoeck & Ruprecht, 2016, page 203.
Compare what this article notes regarding doxa in the LXX and NT: http://faculty.gordon.edu/hu/bi/ted_hildebrandt/ntesources/ntarticles/bsac-nt/harrison-lxximportance-pt2-bs.htm
and He beholds the image of the Lord: This refers to a vision of the “back,” as it says,“and you will see My back” (Exod. 33:23). - [Sifrei Beha’alothecha 1:42:8, Tanchuma Tzav 13]
ותמנת ה' יביט: זה מראה אחורים, כענין שנאמר (שמות לג, כג) וראית את אחורי: