This is a one-liner that appears to originate from Andreas. I'm not clear on why trail first isn't the same as the current position, but I checked and Eddie is right that the actual movement of the HandMorph occurs AFTER this so the current position will be the start position. I loaded this code and it appears to do the correct thing.
If this somehow breaks Genie then I'm of the opinion that there is a bug in Genie and/or it is working around this bug and simply needs to be updated to reflect this fix.
Ken