Interesting results. no real change.
I think alot would depend on body type too. Ectomorph or tall guy doesn't train they get skinny fat real quick.
A lot depends on genetics. But a real genetic skinny person won't get fat without a gym, they'll just slowly lose muscle. I know this all too well. In general, the body always strives for homeostasis, the threshold of mass that it can maintain without training is different for everyone. Diet also plays a HUGE role here. And hormone levels of course.
Btw, I think Evan Centopani once said that without training, the muscle groups that we genetically have the weakest shrink the fastest, an interesting theory and true in my opinion.
Flex500, you have great arm genetics either way.