Reality has a surprising amount of detail (2017)

Welcome to analog IC design. It's all "everything affects everything" kind of situation, especially so at high speed or deep submicron process.

I tried my best to explain to my programmer friend (who ironically works at Intel) why we use dummy transistors in the layout - to no avail.

If university and work taught me something, it's that you can't just handwave some details for later; sure planning everything ahead isn't possible, but if you have not even a hint of how to solve a problem however minor, you won't when it comes to solve it in the future.