Like many things, it depends. This newly released setting is designed to prevent more than the given amperage from passing a given point. Hopefully, there is an upstream breaker that would trip if you pulled an unsafe amperage through it. If you exceed the setting this curtails the onsite generation sources, so that the conductors do not overload.
Say you had a PW+ and a PW and were still using the GW2 for whatever reason in your 200A service panel with just a 200A main breaker. All your PV and ESS sources are inside the GW2, for a total of 80A (50A+30A) of generation breakers. The code (2017 NEC 240.2`.B.2.2) says that wherever your essential loads subpanel occurs, that subpanel must have an OCPD protecting the panel. This is because the combination of your 80A of onsite generation and your assumed 200A grid connection adds up to more than the 200A rating of the essential loads panel and the GW2 and the wire. Therefore putting a 200A main breaker or "Panel Control=200A" on that essential loads panel prevents the addition of grid sources plus PV+PW sources from exceeding the 200A circuit rating. If you were to try to pull 240A from that backup system, the main 200A breaker in your 200A service panel would trip. If "Panel Control" wasn't set, then the PV and PW generation sources would happily supply the additional 40A that the main breaker could not supply. This may overload your 200A conductors or 200A distribution bus of the essential loads subpanel because of the nature of the load side tap within the GW2.
There are several ways to set up PCS settings, and this one is in addition to the other import/export controls. The typical use of this setting is to replace the need for a main breaker in an essential loads panel. Since PCS are already so edgy in NEC 2017, we have chosen to not really use this, and instead continue to use the main breaker in the essential loads subpanel. Import/export control is what we more often use for our systems, since preventing panel upgrades is a $4k win for the customer.
In those cases where we have no choice since a panel doesn't take a main breaker, we would consider using this setting. In that case it would satisfy the requirement shown in 2017 NEC 240.2`.B.2.2
The 2020 NEC will be code here in less than a year, and we can go PCS crazy then. In the meantime, I am satisfied not using this particular PCS setting.