For items that are currently in a state of processing (e.g. Folio effective location of SUL Tech Processing), we use the availabilityClass stored in the Location details to display "In process" to the user. Here's a screen grab from https://searchworks.stanford.edu/view/in00000071192
When the user clicks Request, and the see the Item picker, we're not using the Location availabilityClass. It looks like we're translating the loan policy for the effective location, so the user sees "In-library use only".
Talking with Chris, he suspects we're displaying what we get back from Folio in this particular call. We may need to do something "fancier" to bring consistency to the status display.
For me, it feels important to show an "in process" status in the item picker, because that gives the user valuable information for the request. Of course, we do a lot behind the scenes to rush the item through processing. But it could take a little more time than normal and the status could help the user understand that.
Also - showing "in-library use only" will be incorrect more often than not. Most of our materials circulate, but this effective location is associated with "no loan" in the circulation rules because it's "safer" when applied to all the materials that go through this processing location.