My cat has her designated water bowl, but for some reason, she largely prefers to drink from a 30 cm (12 in) tall water buckets around the house, while standing on her back legs.
Is it normal?
Yes, this kind of behavior is normal for cats and dogs, but it has nothing to with standing on their hind legs.
See, the water in the bucket simply tastes different. It may have a different source (rain water instead of tap water) and a different chemistry due to standing outside for days compared to comming fresh out of a water pipe. It's actually common for pets to prefer "old" water over fresh tap water.
Another reason for this behavior could be the container itself. Whether your cats water bowl is made of plastic or metal, it can influence the smell and taste of the water.