He has no rationale. Doubt he even knows the scale at which MS' tech stack is used, especially outside of the USA's hipster bubbles.
"Boring" industries like insurance might not seem innovative on the outside because their members aren't blogging and twattering about it constantly. One of my clients does catastrophe modeling, and uses both Python and .NET (F#)...but it's probably not going to be something on your radar. But guess what, they're raking in the dough while actually being innovative, yet you're here on HN claiming they're not proper engineers.
Best of luck to you.