I don't know maybe it's just me but I don't consider diarrhea and loose or pudding stools not to be the same thing. I get the feeling many people consider the terms interchangeable. I personally do not. IMO diarrhea is frequent bouts (3x or more) of watery/loose stool in one day with urgency. If it's one or two watery/loose pudding stool in a day I don't consider that diarrhea. I consider that loose stools. Especially if it isn't consistent. IE: one poop is loose and the next is solid and the next is soft poorly formed and there is no urgency.
Frequent watery stools (diarrhea) lasting more than one day is usually a sign of greater illness. Be it viral, bacterial, parasites, parvo, EPI or sibo etc.
Reacurring or occasional bouts of soft pudding stools (loose stools with no urgency) and the occasional watery stool mixed with normal stools is usually less serious in most cases. More indicative of parasites, IBD, stress colitis, food sensitivities, ate something they shouldn't have, etc.
That said: yes my dog has a very sensitive stomach. Anything can set off loose stools for her. I don't worry anymore (after nearly 4 years) unless the bouts last more then a few day. Obviously if I see blood, heavy mucus or is accompanied by any vomiting, lethargy and or fever then it's off to the vet.
I can say that our GSD is the first dog I have ever had that such issues on a regular basis. All of our dogs of past almost never had diarrhea or loose stools and eat everything and anything.