I’m not sure that’s true. Last Office I bought was “Home Edition 2016” and it’s been running on a machine that doesn’t have internet access since 2017 without any issues.
If I block it from accessing Microsoft domains in Little Snitch, it goes into readonly mode after about a month. Opening a hole in the firewall lets it start working again. Previous versions from several years earlier didn't do that.
Microsoft doesn’t release an Office version every year. They technically released 2019, 2021 and 2024, but they have all been “Office 16” versions. As far as I could tell they are more or less “service packs” + random improvements/small features on to of the 2016 base. I was planning to upgrade last year but life got in the way and I only use that machine in the deep winter. Do you know what release they introduced that in?