Hi
From what i can tell the current ArcGIS REST API does not support the ISOWeek function yet. And there doesnt seem to be anything planned regarding supporting it.
I have a possible workaround for your problem...
You can consider a "helper" survey with embedded links in it to open the Inbox of your survey in question.
In my "helper" survey I open the Inbox with specific parameters such as the week number which you seem to be able to calculate within the survey (https://community.esri.com/t5/arcgis-survey123-questions/how-to-calculate-the-week-number-of-a-date/...)
Once you have the week number you can build a URL to open your Inbox with a week number whereclause:
concat('<a href="',concat("https://survey123.arcgis.app/?itemID=<itemid>&open=native&folder=inbox&update=true&download=true&q:where=WeekNumber=%27",${WeekNumber},"%27)"),'"><div style="color:blue"; >Retrieve Data for this week</a>')
This assumes your WeekNumber field is a string - which you should be able to change to an integer in the URL if required
