Those damn lights are terrible. We have them in Auckland where one authority controls motorway a (freeway) an another the local roads. The lights cause banking up at on ramps, blocking local roads. The motorway flow is improved, sure, but local single lane roads become impassable for hours. The lights just shift the problem here in Auckland.
That's an annoying aspect of trying to retrofit old roads with new tech. Roads designed for ramp metering (in Australia at least) have much longer ramps, both before and after the signal (enough space after for the car to accelerate to the speed of the motorway from being stopped, and before to stop the queue clogging surface streets).
But, it could also be a problem with the algorithm they use. The more simple algorithms generally don't take queue length into account, but ALINEA/HERO, which we use in Victoria has queue control.
The lights just shift the problem here in Auckland.
This is exactly their intention, and it's exactly what it does in the Minneapolis area -- it adds a natural saturation point to every onramp, eventually leading to lots of traffic simply using surface roads.
