I noticed people saying they use such tools to open applicant attachments in the context of employee hiring processes.

Isn't it simpler to just open these untrusted files in a cloud service like Google Drive or Microsoft Office online?

[1] https://blog.invisiblethings.org/2013/02/21/converting-untrusted-pdfs-into-trusted.html

[2] https://github.com/freedomofpress/dangerzone