Not necessarily. The word for cat, قطة, ends in the feminine ending as you can see–it is a feminine word. There is a masculine version of it, قط (qiTT), but you could still refer to a cat that you know is male using the feminine word if you don't need to be explicit about its sex, which I'd venture to say is most of the time. It's the other way around with dogs, the default word (كلب, kalb) is masculine and you can use it to refer to female dogs.
Well, I didn't see that discussion. One doesn't read ALL the discussions for the exercises, does one? Anyway, thank you, Hadriel_Eyn, for mentioning this. At least now I know it's not a Duolingo fault, but a naturally occurring phenomenon in Arabic speech. This was corroborated for me by the transliteration into Arabic of "blouse", and the pronunciation /lapitop/ for "laptop". At least, I assume that last wasn't a fault in the Duolingo audio?
..for 2 months of studying Arabic - I read up to 80% of all discussions, just because I wouldn’t miss anything important, and I’m pretty sure that the version of the invisible vowel for connecting words (it makes the pronunciation more melodic, easier and faster) - one of the local moderators wrote, so yes, that last wasn't a mistake of Duo’s artificial voice.
You say, "it makes the pronunciation more melodic, easier and faster". These things are not objective facts. They vary from language to language. In English, for instance, the populace inserts what's called an "intrusive R" presumably because of an aversion to two vowels side by side between two words, so that for instance, "law of the land" sounds the same as "lore of the land". Generally, English speakers who are not linguists are unaware of this. I wonder if Arab speakers are aware of the additional vowels they pronounce. Concerning reading the discussions: it's often a waste of time because a lot of people ask questions, and it's obvious they haven't read the "tips" given for the lessons.