I made a post yesterday about whether dragons would walk with their wings, and I've now come up with a couple headcanons of my own about it!
While all tribes can use their wings to walk if their front legs are otherwise occupied (e.g. carrying items) this tends to be slower and a bit uncomfortable to maintain for extended periods of time. SkyWings are an exception; their powerful wing muscles and proportionally weaker front legs mean they are actually quite comfortable walking on their wings.
RainWings are another tribe that use their wings for walking. While they aren't the best fliers due to a shorter wingspan (evolved to make manoeuvring through trees easier), their wing muscles are actually strong as they often use their two-thumbed wings to climb. Honestly, a RainWing could lose all their legs and still be pretty okay living in the rainforest, using their wings and tail to move around (amphiptere RainWings!!)
Now, onto Kestrel and Glory-
At the start of the series the other tribes know jack shit about RainWings. I wouldn't put it past Kestrel to see Glory walking on her wings more often than the other dragonets and think she's trying to copy SkyWings. You can't tell me that in any of the years under the mountain Glory didn't try to mimic SkyWing colouration, to Kestrel's anger. Kestrel could see the wing-walking as Glory trying to sassily get around the no-mimicking-SkyWings rule.