The meaning is different though. The one in the exercise could be a general statement. I would translate "They are fat olives" as "Illae (?) pingues olivae/olivae pingues sunt" in order to avoid creating too much confusion. It could be an alternative suggestion, sure, but I think it would be safer to leave it like this.
That's what I'm talking about, adding alternate translations. It wont replace the current translation, it will go from only saying "The olives are fat" to also include "Some olives are fat", "There are fat olives" etc. And the Latin side will include more options too.
The pronouncing it as an «e», is today typical of Italianate Latin, but was also the way it was pronounced generally in Europe during the renaissance before restored pronunciation became a hot topic (around the time of Erasmus). It’s not classical, but also has an organic charm about it, as it reflects spoken Latin (at that time, maybe starting as early as the 3rd or 4th century). It’s still the way Spoken Latin is taught in Italy, and also for singing choral works in Latin, so I think both forms should be respected/observed at all times: it’s not an error to pronounce the diphthong as an «e», nor it is Classical Latin to pronounce the diphthong as «ai» as opposed to technically correct «ae», which is ever so subtlety different.
Two modern Latin speakers should still understand each other, and neither of the two forms are either correct or incorrect in the context of just speaking it colloquially.
For now, our goal is to speak it, and write in it; a goal that this course will help us achieve regardless of which pronunciation we choose, in other words, «suum cuique».