Testing this in the terminal I find that the VST3 names appear as long numbers. Only occurs with VST3 names.
rprint(renoise.song().selected_instrument.plugin_properties.available_plugins)
...
[29] => Audio/Generators/VST/Piano V2
[30] => Audio/Generators/VST/TAL-BassLine-101-64
[31] => Audio/Generators/VST3/4172747541564953416C617650726F63
[32] => Audio/Generators/VST3/41727475415649534B61743150726F63
...
At least I know the first one should be called something like this:
[31] => Audio/Generators/VST3/Analog Lab V
This happens at least with Arturia plugins. But I suspect it will happen with any VST3 name.