It's not entirely correct. There's a couple of missing links between the Pz IV and Panther like the VK20.01 and VK30.01, the prototype chassis of which was converted into the Sturer Emil. Similarly the Tiger was derived from the VK36.01 -so the relationship shown between the Tiger and Sturer Emil is back to front - and the "Pz VII Lowe" was a parallel project to the Tiger II, not a derivation of it. The Lowe was cancelled in favour of the Tiger II for being too big and heavy.