Hi. I have created a feature class in ArcGIS Pro which I subsequently uploaded to ArcGIS online as a Hosted Feature Layer in preparation for a field collection campaign. Not too tricky - in this particular point type feature layer I want the field personnel to add a point, add some text fields and THEN have a field with a drop-down with a coded value domain so as to constrain options and make it easy. Easy enough - I created a Text field and assigned a coded value domain with four values to it (in Pro).

1) See my custom domain

2) Now set the domain to the attribute
Then I upload feature class as Hosted Feature Layer on AGOL, add to editable webmap and finally open in Collector. And alas, the functionality does NOT work. In ArcPro with the same feature, the domain constrains me to the four codes I set for blind types when creating features in this FC. But in Collector on my Iphone I can type whatever I want.

I'm just trying to add a feature layer to a webmap utilized in Collector that allows field person to flesh out attributes with drop downs. According to ESRI docs (https://doc.arcgis.com/en/collector/android-phone/help/design-layer.htm ; under subtitle Form design) I'm doing the right thing.
Any ideas?
Zach