UPDATE: I ran a test, and it appears it absolutely does treat any bulk import as newly created assets. In MaintainX, I created a Test Parent Location with two Test Sub Locations. Each Sub Location had 1 Test Parent Asset, which had 3 Sub Assets. I deliberately made naming convention issues, and left all of the detail info blank. This gave me 8 Test Assets when I exported the .csv file for that location. I imported the file into Google Sheets, corrected all of the deliberate errors and missing fields with information, then went to import it. As soon as I saw that the ID field was unmatch during the import process, I knew the answer, but proceeded anyway. Sure enough, once I completed the bulk import, that Test Location went from having 8 Assets/Sub Assets to having 16.
This might not be a huge deal personally for my particular use case, but having come from being a maintenance manager in manufacturing in the past, this would be a HUGE issue for data cleanup because it ultimately means that the CMMS admin will either have to tediously edit each and every asset currently in the system in order to preserve all of the history assigned to them, or lose all of that history by doing a bulk import of all of the corrections, and then deleting the previous assets.
This should be a relatively easy fix for the MaintainX devs to add a feature that checks for the ID field during the upload, and compares it to the current database. Any matching IDs would be highlighted during the import process, and they can even simply add a feature to confirm overwriting the previous asset info with the new uploaded one. I know building and coding new features does take time, but for users whose use case requires the preservation of all WO history and downtime tracking, this feature would make data cleanup much simpler for their application, and would be a huge value add.