I managed to get this to work, though it's unclear to me what set of troubleshooting steps worked. My sense is that this is a combination of two problems:
1. The sustain midi message is no longer mapped to the sustain pedal in Piano V2. It appears to be mapped to Pitch Center or Pitch center just happens to be at the 0 index of UI mappings.
2. After restoring the sustain pedal midi mapping, the plugin doesn't appear to send sustain information to Logic.
Fixing #1:
Open the standalone piano v2 app, click the little settings icon in the top right and select the 'Midi' tab. This immediately turns on Midi learn mode, so be careful. At the very bottom of the screen, in the center, there is a Pedals UI, click the right pedal icon and then press your physical sustain pedal. This should create a new sustain pedal entry in the midi config. If you see a "Pitch Center" entry, you can delete it using the key combo "fn + delete." Close the settings sidebar and try to see if your sustain pedal works.
Fixing #2:
Open Logic and try using your sustain pedal with the factory Steinway piano. If it works, then you're probably good to go for using the Piano V2 plugin. If it doesn't, Open Logic Pro => Preferences => Midi and select the "Reset all midi drivers" button. Close the window and retry the sustain with a factory piano. In the plugin you should see a message in the bottom left corner showing sustain going from 0 to 1.
One thing to be careful about is recording sustain at the beginning of a song. If you press the sustain pedal before the song starts to record, you might need to quantize the sustain midi in addition to the notes you played.
