Why these differences in HJ 3-bettor and UTG 3-bet caller's range?

my question is in reference to the hand and solver analysis from this youtube video: https://www.youtube.com/watch?v=Jn2I_Bc575E

A big portion of the analysis of the way the hand plays out (and most hands, for that matter) on the flop involve the differences between the preflop ranges of the players involved. However, as a noob, I don't always understand the reasons that players' ranges are different.

I've included screenshots from the video below, showing the ranges of each of the players. Ignore the proportion of red/green color inside each block, all that matters is the size of each block.

So the differences are:
1. caller has no AA, KK, AKs
2. some differences in suited aces (no A8s, no A6s)
3. No AQo or KQo
4. most notably, caller has way more 22-TT.
5. caller has 76s, 87s, T9s

My questions are: what are the reasons for these differences? In general, what's the principle behind deciding which hands to call with?

Here are my guesses
1. This one is obvious... these hands would be 4-bet instead of called
2. I'm guessing 3-bettor raises these hands as a bluff, which caller doesn't do.
3. This is confusing to me. UTG has about 2:1 pot odds (call 50k to win a pot of 110k), so in general he wants to call with hands that have 33% equity against HJ's range, right? AQo seems like it does, but I guess it's actually 4bet instead of call as a bluff/weak hand, which does make sense. Is KQo just not a call because it's barely 33% equity?
4. Alright, this is the most important, since I'm guessing it's the reason that the commentators say the flop is better for the UTG caller's range, since it makes more sets and pocket pairs instead of 2 overcards? Do these hands have good equity against the 3-bettor's range? Are they being played in a large part to set-mine? It does seem like they have over 33% equity. Why does the 3-bettor not play more of these hands?
5. Perhaps this is a minor trade-off between having A9s, A8s, A6s as weak hands to balance the range/cover the board and using suited connectors for the same purpose?

The 3-bettor: The 3-bet caller: