OK... Why do we see a certain amount of foreknowledge of foreknowing in the OT, with YHWH (yet not complete or completely, for reasons already stated as to why YHWH cannot completely all-knowing)... Anyway, "why" do we see a "certain amount of foreknowledge or foreknowing with YHWH (and Christ) in both Testaments...? I think, it is not only because he did "just have" a certain (yet limited to compared to the true Father, or the God spoken about in the OP) (yet way more than any of us)...
Anyway, I think it is not only because he just "did have a certain amount of foreknowledge or foreknowing" (or insight) into things (people, places, events, situations, circumstances, ect) at times, but, also that he (YHWH in the OT, and Christ in the NT) also was continually going to the Father and getting "downloads" (so to speak) from him (the Father), as to what was "next" or what was to come "after" following "prior instructions" from the Father before that, or what he was told before in a previous "download" from and/or with the Father, or what was revealed from or by going to him (the Father) in prayer (or communication) (or communing with the Father) before that...
He (YHWH and Christ) never did his own will, but only the Father's always, and this is why we can see much "providence" or a "providential nature" to and with God (them) (in the OT) with "people, places, events, situations, circumstances, and happenings", ect... Cause that has the fingerprints of God the Father "all over it", and is one way we can discover the Father through the Son (YHWH in the OT, Christ in the NT)... With Jesus in the NT we see this as well, and for the same reasons as YHWH in the OT (that is, by his/their continually getting "downloads" (so to speak) from the Father, as to what was next, and sometimes after it and that, ect.)...
But the Father never told YHWH or Jesus "all of everything all at once", or at one time, but did in it all in "steps" and/or "phases" with him (his Son) (YHWH in the OT, and Jesus in the NT)... This also stands to reason that, at times, that "they" (YHWH/Jesus) may not have "completely understood" sometimes, (in that way being like us) but had to have "faith" and keep (the) faith and not stop doing what he/they was/were told... With Jesus, as to his "specific words" that he was speaking or spoke at the time and/or in the moment, (or in the "heat of the moment", with like the Pharisees) I believe those came directly from the Holy Spirit in him, or within him... That is "of and from the Father" (also) and is his (the Father's) spirit, and also the Son's spirit also then also, and is also God himself, also...
But they (YHWH and Christ) were always and continually doing the Father's will as their own will, but it was the Father's will and the Father's plan was involved and is why we see a great deal of providence and providential nature to God, especially in the OT, that has the Father's fingerprints, specifically, all over it... But it was the The Father's will "for the Son", as our God, "for us" as his (the Son's) people... It was the "Father's will for the Son for us"... IOW's the Father's will is not for himself, but is "for the/his Son (YHWH/Jesus) for us"....
And this is important to keep in mind when looking at it or examining it, (their/God's will) (or plans or providential nature or "whatever") (character, personality, ect)...
God Bless!