In addition to the answer from @Yellowhammer, this appears to be related to the OSX system not rebuilding the AudioUnit cache after installation. I found the same issue in Waveform, where the AU Effect did not show up, even though the AU Instrument was appearing. VST/VST3 appear right after install in Waveform, but of course that doesn't help you in Logic (AU only).
I'll look into this, as a restart should not be neccessary for an Audio Unit host to see the plugin.