updateRadioButtons() doesn't fails when length(selected) > 1

[ColinFay]

When trying to send multiple values as selected in updateRadioButtons(), {shiny} doesn't throw an error, as opposed to radioButtons() alone:

Error:

library(shiny)
ui <- fluidPage(
  radioButtons("radio", "Radios", letters, selected = letters[10:11]),
  actionButton("changes", "Changes")
)

server <- function(
  input, 
  output, 
  session
){
  observeEvent(input$changes, {
    updateRadioButtons(session, "radio", selected = letters[2])
  })
}

shinyApp(ui, server)

Listening on http://127.0.0.1:7085
Warning: Error in radioButtons: The 'selected' argument must be of length 1
  79: stop
  78: radioButtons
  70: ui [#2]

With updateRadioButtons(), no error:

library(shiny)
ui <- fluidPage(
  radioButtons("radio", "Radios", letters, selected = letters[10]),
  actionButton("changes", "Changes")
)

server <- function(
  input, 
  output, 
  session
){
  observeEvent(input$changes, {
    updateRadioButtons(session, "radio", selected = letters[2:3])
  })
}

shinyApp(ui, server)