Does WordPress run install/uninstall functions on plugin upgrade?

No, the activation, deactivation and uninstall hooks will not be run when the plugin is updated.

So when your plugin is updated the page will still be there (assuming the user has not deleted it), and it will not be deleted on uninstall if your plugin no longer does this on uninstall.

If you want to do something on update, the proper way is described here:

The proper way to handle an upgrade path is to only run an upgrade
procedure when you need to. Ideally, you would store a “version” in
your plugin’s database option, and then a version in the code. If they
do not match, you would fire your upgrade procedure, and then set the
database option to equal the version in the code.

You could then delete the page in question in that upgrade procedure.

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