Yeah that’s a fair point, tutorializing becomes harder if the player is missing the required items.
But, poofing the items into existance, and noting the player about it, solves that. Dwarf Fortress is such a dynamic game, that unless you really restrict the player they will find ways to miss important tutorial items, with or without a custom embark. Trees, water, wild animals, stressed non-wild animals, cave-ins are all potentially lethal to a dwarf, and the last one can happen as soon as you get to digging. Being able to poof forth items, or repair trouble the player causes is pretty much required for a functioning Dwarf Fortress tutorial mode.
I don’t think the Tutorial should direct new players toward the advanced/detailed embark screen. The preset embark works just fine, and players need to get into the main gameplay routine as soon as possible. Especially as world-gen (should the tutorial include it) is time-consuming, even for smaller world sizes. Should a game take several minutes before I even get to the main tutorial I would certainly be more likely to give up and quit.
It’s not like the detailed embark screen needs much of a tutorial either, anyone familiar with any kind of RPG or management game should be aware of the principles behind of a party/item setup. Not being familiar with the items/skills, and it being tedious, is why new players shouldn’t be directed to it.