Roux was born with a rare condition called tranverse terminal hemimelia which caused her to be born without any front legs. As you can tell, this disability does not stop her from getting on with life and her owners say that her mobility is very good and that she is able to function pretty well without her legs.
I hate that article, allegedly by a bio teacher, that says "XX =/= female and XY=/=male, humans are more complex, look at--" and then lists a bunch of rare and terrifying genetic disorders and syndromes, with "syndrome" in their name. Most people only hear about shit like that right before they terminate a pregnancy. It doesn't normalize transgenderism to pair it with syndromes and birth defects, or else we'd all be ok with kids with spina bifida.