It does seem to be an oversight, and I also wouldn't go so far to say it's extremely poor. Tutorials are difficult to create for every eventual outcome without being extremely restrictive or overbearing. Test cases for tutorials are probably even harder, and consist of many "what ifs" for how to ...

Ghost rail planer on LMB click changes plan starting position instead of creating a plan.
What i am doing:
1) Press Shift
2) LMB click on existing rail(without releasing shift)
3) LMB click on arbitrary point on map(without releasing shift