When publishing a S123 form to Portal using S123 Connect, it creates a folder on your content page where it places the survey and the content associated with it. By default, Esri prefixes the folder name with "Survey-" (ex: Survey-Inspection Survey)
When you delete a survey through S123 Connect, it will delete the associated survey folder. However, there is a specific scenario where S123 Connect will delete a different folder and not the associated survey folder.
For some organizations, it is a common workflow to change ownership of S123 forms so other people can make changes and republish them. In this scenario, a user might change ownership of a survey and insert it into a different folder in their content. Note that this folder is NOT the original survey folder that was created when initially publishing the S123 form.
After changing ownership, the person then downloads the form through S123 Connect so they can make changes and republish. However, in the event that the end user needs to delete the survey through S123 Connect, it will delete the folder the survey is currently located in and not the original "survey" folder that was created when the form was originally published.
While S123 Connect gives you a warning that it will delete the survey and the survey folder (along with all of its contents), the wording is misleading as it indicates that it is going to delete the survey folder, which in my opinion, indicates the original survey folder that was created when originally publishing the survey.
Here is the warning S123 Connect gives:

An end user might place the survey in their own folder with other content in it. At this point, I would not consider this the "survey" folder. It's just a regular folder with content in it. And when you go to delete the survey through S123 Connect, it will delete everything in that folder, including non-S123 related content that you do not want to be deleted. This is incredibly dangerous.
My idea is that Esri needs to clarify the wording S123 Connect provides when deleting a survey to indicate that it will delete the folder (and all of its content) that the survey is currently located in and not the "survey" folder which is a little vague and misleading.