"Is the helmsman also controlling the speed?"
On the older ships you had something called a 'motor order telegraph', that big brass thingy with a lever on it, that says "stop, ahead 1/3, ahead 2/3, standard, full, flank" on it [also backing bells]. You'd have one for each throttle. So if the captain says "all back port, all flank starboard" you ring up the appropriate speeds on the indicators, and someone in the engine room operates the steam system accordingly.
If you have 4 shafts, then "all back port" means both of them, and "all flank starboard" is similar. But using 'all' even for a single shaft is common because people recognize that as a speed change order from the Officer of the Deck.
Perhaps the REAL problem here is the use of touch screens for something that was normally a bit more controlled, involved multiple people, etc.. You had to physically operate levers to send an order to the engine room(s) to make something happen. [this also means you can control the ship when the bridge is blown to @#$% and you have someone on deck with a sound powered phone giving orders to the various aux control stations, something that helps with a badly damaged ship trying to deal with it instead of sinking].