Plugin with radio buttons in Premiere Pro using After Effects API

I'm working on an effect for Premiere Pro using the After Effects API, and according to the SDK you can pass the PF_ParamDef.ui_flags style PF_PUI_RADIO_BUTTON when creating your drop down parameter (using PF_Param_POPUP) to have it shown as a group of radio buttons.  The documentation and the comment next to the flag both say that this is picked up by Premiere but ignored by After Effects.

However: I tried this, but Premiere (both versions 2018 and 2023 at least) just refuses to pick up the style and shows a dropdown anyway.

Is this a known bug?  I googled for PF_PUI_RADIO_BUTTON and it gives a grand total of six hits, all linking to either that documentation or to copies of the API header file.  Maybe no-one has ever used it so that this bug could have flown under the radar for so long?