You can see in this video [attap.umd.edu] how movements are handled.

It's nice to see someone interested in complex urban interchanges

On a regular MUT/Michigan left, you are right, all cars willing to turn left have to go straight then take the u-turn ramps.

Here is a Google Maps link [www.google.fr] showing one of these interchange on the I-96 in Detroit, so that I can explain better.
Contrary to a regular MUT, the Jeffries Fwy does not directly intersect Middlebelt Rd (obviously). There is only the Schoolcraft Rd, which is a one way frontage road, that does.
When you're at the green light on Schoolcraft Rd, there no car coming from the front as it is one way. Therefore you do not have to cross any vehicle pass when turning left, this is why left turn is allowed from Schoolcraft to Middlebelt. You can clearly see in streetview that left turn are allowed.

I will also add a recommended lane distribution to clear this up. Hopefully when I get around to doing a cleanup of the assets this weekend!

I've added TM:PE to the required items, as you're right that this is useless without it.

However, traffic leaving the highway to then make a left turn should be FORCED to proceed straight and use the "Roundabout" part of the interchange. From what I gather, the theory behind these interchanges is that there are only two intersections with lights, and those lights only allow traffic to go straight (or make a right turn that doesn't cross anything), meaning that there are only two light phases alternating rather quickly.

I referenced the government documentation for that part,
"The signals at the main intersection and the crossovers in an MUT intersection design have only two signal phases because direct left-turning traffic at the main intersection is redirected to a U-turn [along the roundabout portion]. Much of the efficiency gained from installing MUT intersections stems from the two-phase signal operation."

I'm curious as to how much the left turn changes the traffic flow.

Note that traffic coming from the highway can make a direct left turn on the main bridge, they do not have to use the "roundabout ramps".
Also you could add TM:PE in required mods because without it it's pretty useless ^^

Yes, they are the same :D

This is supposed to be styled similar to the MUT, I'm unfamiliar with the I-96
https://www.fhwa.dot.gov/publications/research/safety/09057/index.cfm

I'm currently making a service interchange like this one, a mix between a TUDI and a Michigan-left. It's one of those on the I-96, right ?