I don't know about Proxima Centauri b, but they'll be spending around 25% of "Cycle 1" (the first 6,000 hours of science) working on exoplanets, don't worry:
"Over the coming year, researchers will use spectroscopy to analyze the surfaces and atmospheres of several dozen exoplanets, from small rocky planets to gas- and ice-rich giants. Nearly one-quarter of Webb’s Cycle 1 observation time is allocated to studying exoplanets and the materials that form them." - https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-...
"Over the coming year, researchers will use spectroscopy to analyze the surfaces and atmospheres of several dozen exoplanets, from small rocky planets to gas- and ice-rich giants. Nearly one-quarter of Webb’s Cycle 1 observation time is allocated to studying exoplanets and the materials that form them." - https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-...