'hovertemplate' not passable as an attribute into a dataframe in a sankey diagram's nodes/links

The 'hovertemplate' attribute is not working when passed into the 'nodes' or 'links' dataframes in a sankey diagram. "Node" and "link" are arguments for the sankey's links and nodes and are of type dataframe which contain arbitrary data for the links and nodes, as well as attributes of links and nodes (see plotly::schema() for a list of all available attributes for each trace). Reprex here is unnecessary since my question is why 'hovertemplate' cannot be passed into the 'nodes' or 'links' as attributes when other attributes such as 'color' and 'hoverinfo' are passable? Is there any workaround to this?

fig <- plot_ly(
      type = "sankey",
      orientation = "h",
      node = nodes, # dataframe which includes sankey trace data and attributes
      link = links, # dataframe which includes sankey trace data and attributes
      valueformat = ".0f")

fig 

No implementation file or test is named. Start by inspecting plotly::schema() for Sankey node and link attributes, then trace how the node and link dataframes are converted; done means determining why hovertemplate differs from color and hoverinfo and documenting a confirmed workaround or supported behavior.