Is it possible for an upgrade to automatically replace deprecated plugin smart service nodes?

Can an Appian update cause deprecated third party nodes to be replaced with new out of the box nodes?

It sounds like a crazy question i know. So I had a really weird experience today. 

We are using a deprecated plugin in one of our process models called excel_export (v3.1).

2 months ago, it got removed accidentally, breaking our functionality.  It has ? marks over the icons, and upon re-adding the plugin, its node art came back and functionality resumed.

I put a task down to replace the plugin with existing functionality and ignored it for 2 months.  We upgraded to 19.3 today

I took another look at the process model today, and suddenly the nodes using excel_export deprecated smart services where replaced by  out of the box nodes(with the same name) that did not exist as options 2 months ago as out of the box nodes!

The 2 smart service nodes that where replaced are in the screenshot.

Can this happen?  Or am I going crazy.  I am disabling the plugin again this week to see if the functionality cuts off again. But looking at this 2 months later, I don't think it should.

Oh, also there where no sneaky developers editing this model.  I checked the history and am basically our sole developer.

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