Interesting point, but to OP's point- This wasn't true when Office was first introduced and Office still created a domineering market share. In fact, I'd argue these moat-by-idiosyncracy features are a result of that market share. There is nothing stopping OpenAI from developing their own over time.
Spreadsheets are as much a calculation environment as they are a table of figures, and if you're technical enough to be writing docs in LaTeX you should be doing the calculations in a more rigorous environment where you don't copy the formulas between cells.
Plus most analogs would require additional procurement, to which the response for most business users would be "No, you're not a developer."
It was absolutely true at that time, but Microsoft was already a behemoth monopoly with deep customer connections throughout enterprise and was uniquely positioned to overcome the moats of their otherwise fairly secure competitors, whose users were just as loyal then as the GP is describing about users now.
Even if OpenAI could establish some kind of moat, office applications make for very poor analogy as to how they might or whether they need to.