This will not answer the question but state some further facts about the LXX of Ps 22/21 verse 1 (throughout I will use English verse numbers).
This is yet another instance of the LXX and Masoretic text differing.
אֵלִ֣י אֵ֭לִי לָמָ֣ה עֲזַבְתָּ֑נִי רָחֹ֥וק מִֽ֝ישׁוּעָתִ֗י דִּבְרֵ֥י
שַׁאֲגָתִֽי = My God, My God why have you forsaken me? Why are you so
far from saving me, from the words of my groaning?
LXX text (Swete, Brenton, Rahlfs all the same):
Ο ΘΕΟΣ, ὁ Θεός μου, πρόσχες μοι· ἵνα τί ἐγκατέλιπές με; μακρὰν ἀπὸ τῆς
σωτηρίας μου οἱ λόγοι τῶν παραπτωμάτων μου. = O God, my God, attend to
me: why hast thou forsaken me? the account of my transgressions is far
from my salvation. (Brenton Translation).
Aramaic (From Matt 27:46)
Ἡλεὶ Ἡλεὶ λεμὰ σαβαχθανεί;
Greek (From Matt 26:46)
Θεέ μου θεέ μου, ἵνα τί με ἐγκατέλιπες; = My God, My God, why have you
We observe several things about this comparison:
- The Greek of the LXX is different from the Hebrew in several respects. The LXX adds the phrase "attend to me" and the last part of the verse is very different.
- The Aramaic is much closer to the Hebrew
- Matthew does not quote the LXX but translates the Aramaic.
I offer no comment on the reason for these differences - the LXX is different from the Hebrew, the Aramaic and the GNT. It is definitely the "odd man out". (I have seen this on dozens of occasions with the LXX.)