I don't know what the real answer is, and I think it also has to do with your weather.
I have 2 mommas right now with their goslings, and they are outside with them after 3 days, but they really baby them for a week. I was amazed last week when we had a snow storm (more like a short rain storm, but with snow and wind instead) come through and one momma laid on the ground, facing the wind, and put her babies behind her wing as a wind barrier (2 weeks old), and the other momma and her babies just kept munching on the weeds (3 weeks old).
the 4 goslings we are hand raising are "outside". There is a lean-to next to the chicken coop with a heat lamp (2 extension cords are ran out there). Not insulated, not water proof (they do have a spot to get off the ground). We keep them in there all night, runs about 75-80 the last couple of nights directly under the light (30 at night). During the day, I crack open the run door, and they go back and forth. MIL goes out their 4-5 times a day (more if the weather is nice) and walks them around to get more weeds/grass, and play in the pond. They have a little dish to play in the run also. This is being done even though we were in a winter storm this week, and outside temps never got over 35 and the wind and snow was flying for the last 4 days.... Our goslings are 2 weeks today.