Hola Sky

I understand your point, but bear in mind there are different ways to teach and learn specific topics. In my experience as a teacher I've never added the information about those conjugations not having the vowel change because the stress is not in that first syllable. Sometimes students who are still beginners find it difficult to realise where a syllable is stressed, and by seeing the Spanish word written they don't quite get the intonation of the word, so there are some bits of information that are best left unmentioned in my opinion in the lower levels. 

 I've always found that the simple indication of not changing the vowels in the nosotros and vosotros forms is enough for students to remember the rule. Other teachers find very useful to mention that if you conjugate this type of  irregular verb in the present tense by writing it in two sets of three, so:

yo quiero                   nosotros queremos

tú quieres                  vosotros queremos

él quiere                    ellos quieren

and then you draw a line forming the shape of a shoe/boot, i.e. leaving nosotros/vosotros out, you can see clearly by visualising that shoe/boot, which conjugations do not undergo the vowel change. 

Sorry, I can't include a screenshot here to illustrate. 

So, explanations do vary, but I think they're all equally valid. 

Un saludo cordial 

Inma