Bob, are you working in a project with a number of maps/layouts?
If you were to open an Untitled Pro project and work with the same dataset, what do your performance numbers look like?
While it is expected for processing to take longer with Enable Undo on: Undo geoprocessing tools—ArcGIS Pro | ArcGIS Desktop
Performance and scalability
When geoprocessing tools are run in an edit session, performance will decrease compared to when the same tool is run outside an edit session. Similarly, scalability will decrease, as fewer features can be processed in an edit session compared to outside an edit session.
the example you're giving of 32 minutes doesn't seem right.
I just did another test
ArcGIS Pro 2.4.2
49,542 points in shapefile.
Calculating Long field.
Enable Undo on = 1 min 14 seconds
Enable Undo off = 47.45 seconds
Are you able to provide a project package that we could use to investigate the performance you're seeing?