I've only ever gavage fed sick adults, so fair enough on that one. As I'm sure you know, my flock has needs that have required literally thousands of medication administrations on a semi-regular basis over the years. I'm just really glad crop tubing is in my emergency skill set, because according to several vets I've known, needing to be tube fed is the second most common reason for birds to need hospitalization (#1 being blood loss from broken blood feathers).
I do sort of think that anyone who has birds but might not have readily available emergency vet access would benefit from learning blood feather first aid, gavage feeding, and nasal flushes.
I guess my take-home point here is that I don't think it's at all unreasonable to suggest that people try it in an emergency. It's definitely better if you can have someone show you how in person, but I think it's totally doable from a diagram or Youtube video in a pinch. When I learned, my vet described it and then just had me try, because a) it's kind of a hands-on thing and b) it's really not risky as long as you're not using force against resistance.