Hi Michael
Thanks for your reply and for clarifying you're accessing the survey in ArcGIS Online. As you've covered with Support, selecting the field app link option provides a short URL that will launch the survey in the field app, with the intention that this URL can be distributed to those users who will be submitting data. As you've already discovered this does not affect the default behaviour when clicking on the form item in ArcGIS Online.
Disabling the "Create web form" option as suggested on this thread by mark dynge is useful in that it would not be possible for users to access a web form version of the survey (as no such version would exist); however, this also does not affect the default behaviour when clicking on the form item in ArcGIS Online or the default survey link on the Survey123 website.
If users are going to launch the survey from ArcGIS Online, one option could be to add the field app URL as a hyperlink to the item description on the form item's Overview page, or advise users to use the Open in Survey123 app option from the drop-down in the top-right.
We have an open enhancement request to improve the handling of surveys on the Survey123 website when they are published from Connect with the web form disabled.
Best regards,
Jim