I was being less technical with my terminology for a layperson audience - but to clarify - these are derived from induced stem cells, which are cells engineered to go back into a stem type state, which means they're basically induced to be cancers. These are not zygotes from germline fells formed in the niche where they are supported to differentiate correctly etc. IPSCs are not embryonic stem cells, and even ESC derived stem cell lines have been growing so long in culture that they do not behave like germline cells. And even then, the method of differentiation and control is not what happens in normal development, we're sending them different pathways. Turning somatic cells into stem cells is fundamentally giving them the ability to proliferate, and their failure to differentiate into the cells we want shows a failure to control them. Like I said, this is a known problem and one with significant investment behind it as people are finding better and better ways to isolate artificial pancreases to prevent the (currently) inevitable carcinogenesis of these ipsc derived cells