Years ago I worked with USFS to show the flow to/from a GPS and the end result - a file saved on disk. See https://www.fs.fed.us/database/gps/aboutgps/documents/nad83.pdf
This may look complicated, and out of date, but it is. But, fast forward to new reference frames, hi accuracy devices, new projection libraries, new transformations both inside Arc and on AGOL, Feature Services, Location profiles, Exporting from AGOL for files, ArcServer, you have a monster. But to train persons, to instruct the right way the community using Collector needs a flow chart/document that does the entire round trip. People using Collector in the field are at the most basic level are trying to store data collected on a device with measurements coming from space with our without augmentation and storing the data. You could develop this type of POSTER that we can use.
Could the Collector team combine forces with Melita Kennedy and do the same? I'm not asking for a repeat of "hi accuracy" documentation, or "When using this device, do this". GPS field nerds dance between a GIS stored in some reference frame and are trying to jump through the datum hoops BACK to the GIS. What is failing, and compounding the datum confusion is collector documentation stops at AGOL. I suggest a diagram, document, flow chart that completes the entire round trip.
The data managers need to see this (the ones administering the data), field users need to see this (the collectors). It is imperative for metadata with 2022 coming in just two more years, that those using collector has to know what the data is "in". Because Collector cannot do Project on-the-fly transformations, along the way from GIS to the field, back to GIS (EXPORTING a shape or FGDB or direct consumption into ArcServer, the world needs to know what kicks in and where.
I hope this idea gets some likes. Being a trainer, we need a POSTER hanging on a wall showing where people are, where they are going to be, and where they are going to end up back in the GIS. Don't stop at collecting, don't stop at AGOL Feature services, complete the round trip into GIS. Do this, and all the Datum questions you get on a daily basis can be directed to this document - written and layed out clear enough that someone in Canada (CSRS), United States (NAD83 (2011)), Hawaii (NAD83 (PA11)), Botswana (?) can plug into.
Thanks for the opportunity to enter this idea.