Question to the tribe: My 2020 SR5 is rwd in 2H. Goes around sharp corners on dry pavement just fine, no skipping/binding in the rear. The inside tire is traveling 'less' than the outside tire and my understanding is the limited slip differential makes that happen. But when I switch to 4H or 4L, that capability goes away and I get skipping and binding when turning at full steering lock.
Why, oh why? Does the TRD model do this?

You do not have a limited slip rear diff from Toyota. So unless you've changed the rear differential you have an "open" rear differential. It does have traction control though that will help if it starts slipping, but that is applied by using the brakes. Your SR5 does not have a center differential at all. It has a fixed or "locked" transfer case engagement. So when you're in 4hi or 4lo - just like how the right and left hand tires travel a different distance around a corner, the front and rear axles also travel a different distance around a corner. Since your transfer case is locking the front and rear - they will bind and one of the tires will skid some as you go around a corner.

That is why you generally don't want to drive in 4hi unless the road is slippery. (But it will not hurt anything other than tire wear - the drive train is more than robust enough to handle the forces. It's just not ideal for efficiency or tire wear.)

It's a characteristic of all part-time 4WD vehicles. The 4WD system in your SR5 is the same as in a TRD (other than the shift mechanism; knob or mechanical shifter).

The binding is because of the transfer case. In 2WD power is only going to the rear driveshaft. In 4WD equal power is going to both the front and rear driveshafts. When you turn the front wheels go in a wider turning circle than the rear wheels which means they turn at different speeds. Meanwhile both driveshafts want to turn at the same speed. The binding happens when you turn while in 4WD on dry pavement where your tires can't slip. On ice, dirt, or wet/slick roads the tires can slip which allows the front and rear wheels to turn at different speeds while the driveshafts can still turn at the same speed and thus you don't have any binding. This is why the owner's manual states to only drive in a straight line on dry pavement while in 4WD.

In vehicles with a full-time 4WD system the transfer case allows both driveshafts to turn at different speeds (due to a center differential) so binding is not an issue.

Sounds like you expecting AWD.

The SR5 does not have a center differential, so the front and rear axles MUST turn at the same rate, causing what you are experiencing. The Limited has a center differential and will not do that.

Do NOT drive on dry roads in 4WD because you can damage the power train due to the excess stress.

This is a solid and understandable response. Nicely done.

Is there anything as straight-forward posted here (or elsewhere) on the various 5th Gen aids (MTS, Crawl, traction control, ATAC, Rear Diff w/2-4wd modes)? A primer/starters guide, or something for the advanced driver?

I'm to the point of confusion that I'm not really using anything in the rig other than 2/4hi/4lo and/with traction control off, on our local hard and rocky SoCal trails.

Are you putting it in 4H or 4L on the street or dirt roads?

To expand on everything that has been said: it's not just that each side is turning at a different rate, it's all 4 tires -- each tire follows it's own arc when turning.

The inside wheels turn less than the outside wheels, but the rear wheels also turn less than the front wheels so there is a difference not just side to side but also front to back.

If you are driving in snow or sand or anything that leaves tracks, when you make a turn you'll see 4 tire tracks through at least part of the turn

MTS, Crawl and diff lock are Trail, Off Road, Pro versions only.

ATRAC is a tight traction control for 4L only.
MTS is a variable ATRAC, good for sand or snow

It gets confusing, there are good YouTube videos for all

It helps but it also confusing to read the manual

Great link here that explains all the Toyota traction control modes on the Tacoma Forums. As far as I can see, it should be the same for the 4runner - 3rd Gen Traction Control Modes Explained | Tacoma World

Was in 4h on snow, then drove to a covered parking area which was dry. I noticed it then. Thanks all for the great explanations. makes sense.

haha!! Not really. Just curious.

Does anyone have a copy of the "too much friction" video?!

I went to post it here but they made it private!
I think this was the video link: https://www.youtube.com/watch?v=_oHWbyEfUKs

Good one.
Here’s a simplified 4WD reference guide a forum member put together (it’s not a Toyota publication).

https://www.toyota-4runner.org/2791697-post763.html

This

How Tight of a Turn Before Binding Occurs