According to this thread: Are the Arcade FeatureSet functions supported in Collector? it is not yet possible to use feature sets to pass related data from Collector to Survey123. It does however appear to be possible using an AGOL web map. I have tested and confirmed that this works in a web map but does not in Collector.
Although passing related data works fine in an AGOL web map, I'm concerned about connectivity for folks in the field. Ideally, I'd like to utilize Collector to take advantage of offline use, but the functionality for passing related data to Survey123 doesn't seem to be there yet. Is there another way to take a web map offline? Or perhaps there is a different Arcade expression I can use that does not involve feature sets but still passes related data?