subplot - merging titles following ggplotly conversion

data(faithful)

p1 <- plotly::ggplotly(
  ggplot(faithful, aes(x = eruptions)) + 
    geom_histogram(bins = 20) + 
    theme_minimal()  + 
    labs(title = "A.")
)

p2 <- plotly::ggplotly(
  ggplot(faithful, aes(x = waiting)) + 
    geom_histogram(bins = 20) + 
    theme_minimal()  + 
    labs(title = "B.")
)

pl <- subplot(p1, p2, nrows = 1, titleX = TRUE)

## note  that changing to labs(tag = "A.") results in loss of the 'tag' at the ggplotly function.  

I am creating a gglot (histogram, in this case) which includes a sub-panel label. I want to then convert to a plotly figure using the plotly::ggplotly function. The label is transmitted faithfully to each of p1 and p2. However, when combining these into a subplot, the label seems to be merged . I lose the 'A.' label on the first plot p1, generally. The titleX option does not prevent this from occurring.

Inizia con l'esempio riproducibile con i dati faithful usando ggplotly e subplot, quindi traccia come subplot combina i titoli di p1 e p2 quando titleX è abilitato. Conferma il comportamento per labs(title = "A.") e labs(title = "B."); il lavoro è completato quando entrambe le etichette rimangono visibili dopo la conversione e la combinazione.