When the bottom bar is showing:

• Is it properly in the tab order (seems to be)
• Are there any screen reader notifications if the bar appears / disappears or becomes enabled / disabled?

For example, the page says "In the case of forms, only invoke it if a form is in a savable state." You may want to trigger a screen reader event when a form becomes saveable like

you may now save your form by tabbing to the end.