Categoryorder not working when specifying plot type

When using the category order parameter, no plot is generated if the plot type is specified in the plot_ly call:

p <- plotly::plot_ly(type = 'bar')
colNames <- names(iris)
colNames <- colNames[-which(colNames == 'Species')]

for(trace in colNames){
  p <- p %>% plotly::add_trace(data= iris, x = ~ Species, y = as.formula(paste0("~`", trace, "`")), name = trace)
}

p  %>% layout(xaxis = list(categoryorder='total descending'))

With the following warning, which I don't understand since I'm not combining discrete and non-discrete data in the same axis:

Warning message:
Can't display both discrete & non-discrete data on same axis 

If I specify the type in add_trace instead of the plot, then it works correctly and the warning is gone:

p <- plotly::plot_ly()
colNames <- names(df)
colNames <- colNames[-which(colNames == 'Species')]

for(trace in colNames){
  p <- p %>% plotly::add_trace(type = 'bar', data= iris, x = ~ Species, y = as.formula(paste0("~`", trace, "`")), name = trace)
}

p %>% layout(xaxis = list(categoryorder='total descending'))

Maybe this is the intended behavior? If so, why does specifying the type in the traces works and not in the plot? The warning seems unclear to me.

Inizia eseguendo la riproduzione R fornita con iris e confronta plot_ly(type = 'bar') con add_trace(type = 'bar'). Traccia il modo in cui plot_ly e add_trace propagano il type e il modo in cui layout(xaxis = list(categoryorder = 'total descending')) gestisce le trace risultanti. Il lavoro è completato quando la riproduzione non emette più l'avviso e l'ordinamento delle categorie funziona in modo coerente.