The companies I work for while consulting (mainly financial and health organizations) have been very cautious about any company or PII data going to these A.I. programs, and the cloud in general, and are looking to make their own local run generative A.I. LLMs for their employees to use.
By it's very nature these Excel documents will be filled with company data, so I can imagine these companies would also be a bit cautious sending those calculations to the cloud, especially if they can't control the flow of data from their I.T. departments via web applications.
But I'm just a software engineer at the end of the day, and don't professionally use Excel all that much right now (if anything I use it much more for my hobby of board game design). So I can't speak with too much authority on the matter. Just my observations.