I agree that HML requires a very different mindset from hand-written instructions (basically computer code vs "plan English").
I think the curriculum does help the transition by first having students learn to read/trace HML before they write, but I also agree that it's bit jarring/challenging having the first "writing" practice being a relatively difficult algorithm (not many of my students got it either).
If I was willing to dedicate more time to it, I would try giving my students smaller/easier challenges so they get more practice writing with the commands - maybe stuff like "write an algorithm that makes the right hand stop at card value 8" (can even tier that, so assume the card is present, then write code that accounts for the card possibly not being present, or if the card is present at position 0).
The simulator is indeed awesome, but I use it with caution because without the simulator, students are forced to read/trace their own code. With the simulator, some students turn it into a game of wild guessing since it requires no work on their part to "check" their code (although I guess I could say that about any other time students are writing code on the computer...).