Answer: The difference in the icons is best illustrated with a screenshot.
Here are some 11.1.5 icons:
And here are the same icons in 11.1.6:
IBM says this about the introduction of the new icons: “New icons adhering to the Carbon Design principles were introduced in 11.1.6. The adoption of Carbon Design icons provides a consistent user experience across IBM products. For
more information, see https://www.carbondesignsystem.com “
The Carbon Design system focuses on rapidly building “beautiful and accessible experiences”. And it includes iconography for use in these “beautiful” systems https://www.carbondesignsystem.com/guidelines/icons/library which IBM is introducing into all of their GUIs.