not sure what the deal is? when you buy software at some point they stop making updates for it
It has nothing to do with that.
The original EOL statement said that you original app would still work and not disappear from the system and that your files were ok. In the "updated" version (which they made it seem like it was the originally published version and
NOT an updated version) states that only your files would still be opened by "any supported" Office product. Not the one that you got on the perpetual license. No mention that your app would still work or that it wouldn't disappear (if I'm not mistaken, older versions of some MS products have been removed via update channels (Skype for Business to Teams etc, so the delivery system is there for partial or all of this)) from the system in the "updated" version.
Yes, updates stop going has been accepted practice for a long time. This is about a perpetually licensed product no longer working. What was one benefit of a perpetually licensed product? The ability to still use it and not have to pay to upgrade to the next version as long as it would still install on the OS. That doesn't appear to be the case anymore.