as i read the article it is asserting exactly what you are asserting the two example sentences are indeed illustrating the same thing the point the article makes is that different names are used popular language calls this thing singular they linguists call it plural anaphoric they sure it's the same thing i'm not sure where you get the idea of indeterminate number shifting to indeterminate gender i for one agree with you there is no such shift in english unless it lies a long way back in the history of english pronouns but that's another and long story the article however at least as i read it also agrees with us it asserts there are two types of indeterminacy either or both of which can be marked by use of they where does it say one shifts into the other regarding your sentences you have constructed them such that all have indeterminate gender the first however could clearly apply to or people so also has indeterminate number or is plural per giv n the key thing is that all your sentences involve universal quantification over the domain or restriction of a variable for all people or students x in x your sentences assert something that is true for person or student x because there is a plurality of x in x giv n and other liguists call usage of they in constructions such as yours plural because each x is a singular person in the first sentence a hypothetical person ordinary people like you and me call this usage singular in fact though these constructions are distributive one assertion to each of many people which is why grammatical number cannot be well defined there is no specific reference so singularity or plurality can't be derived from a referent in the usual way the constructions have either generic reference or no reference at all