In my experience, I hear and see "notes" and "footnotes" used interchangeably when referring to financial statement notes. I've also not heard anyone react negatively to someone using footnotes instead of notes. Have you run into many people who insist on using only "notes"?
For reference, I've worked in finance for several years (investment banking and as a professional public markets investor [hedge fund]), and I also have a PhD with a focus on capital markets disclosure.
A quick search finds many examples where "footnotes" is used by the SEC [1], the FASB [2, 3, 4], the CFA Institute [5, 6], KPMG [7], and Investopedia [8], to name a few. I also saw several papers in both The Journal of Finance and The Accounting Review that use the term "footnotes".
Not OP but presumably because footnotes are a hack to hide away things you don't want many people to look at [0]. Enron was famous for this and I suspect many fraudulent companies do the same.
Its also quite common for FS to have actual footnotes (ie in bottom margin of page) in addition to notes.