A Vendor Lock-In is when certain software is developed to be incompatible by design with other software that have similar functionality. It is used to establish a monopoly. And any such function is malicious.
This comment thread is for people to document various implementations of this malicious feature.
I don't know if you know but Flow was in fact done using Blender. At the 2024th Blender Conference the head of the animation department on the film Silly-Pélissier Léo even presented a talk about this. ( available on PeerTube )