This was really helpful , thank you.That you would ask this question, yet proclaim yourself to be on the "high ground" regarding English rules, to send anyone who disagrees with you "to go to your local school or college and ask an English teacher you trust", when you NEVER provide any evidence to support your claims, is just astonishing.
I don't have a degree in English, but I've been using the language for 57 years, and I've been reading books in English for about 53 (?) years. And when I did my primary training in Greek, the textbook I used put a GREAT amount of emphasis in teaching English grammar, as a precursor to teaching Greek grammar, because let's face it, English grammar has been put on the back burner in North American schools for the past 20-30 years.
In the school where I teach, we have a significant number of ESL classrooms. And both the ESL instructors and the credit course English teachers come to me with questions about grammar, because they recognize I know something about them.
So yes, the following pairs of sentences are semantically equivalent.
"I am breathing."
"I am presently breathing."
"I was a student in high school."
"I was a student in high school in the past."
"I will be a university graduate."
"I will be a university graduate in the future."
There is no difference in meaning between the two sentences in each group.
The latter sentence may be thought of as an "amplified" version of the former sentence, and each addition is FULLY justified based on the verb TENSE.
THAT'S. HOW. VERB. TENSES. WORK.