If you use the described method in that thread, it will let you to combine the workforce assignment and your survey from in one place, without any need to use two apps. your users will be able to see all the information and create the assignments with the attachment in the same place,I'm not sure If this is will be fine with workflow though.
you can integrate the two apps and pass some of the information for your project from the advanced option tab. keep in mind that the attachment field is not listed for this option, that's why I suggested the other workflow.
or have a look on the following thread which describe how you can pass some information to your survey from, maybe you can test that with the attachments field. Prepopulate answers—Survey123 for ArcGIS | Documentation
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