I think there may be a problem with this in the new Survey123. Here's my workflow for repro:
1. Create a basic survey on the website. Easy to drag drop and get started before adding all the fun stuff. Publish.
2. Open Survey123 Connect and download and open the Web Survey.
3. Try entering null into the bind::esri:fieldtype box. ERROR.
It looks like validation is looking for esri fieldtypes on the same worksheet ('=$A$155:$A$162') and not on the types sheet or maybe it's supposed to be somewhere else.
In the Constraints Sample, the data validation is pointing to '=types!$A$141:$A$149', which has all the field types.
Just to be sure, I checked another survey that I created online when I was having trouble with the GRID syntax (still am, honestly...), and that also had the data validation referencing the current (survey) worksheet and not the types worksheet.
So, long story short: the XLS created from an Online Survey does not have the right bind::esri:fieldType Data Validation reference. I'll submit through support but just in case anyone else runs into this problem.