Maybe relevant: looking at the IGE resource you linked, I noticed it's from the UK and wondered if maybe the "basic" tense system model has regional differences. So, I did a search for "6 tense system" to see if anything would turn up comparing US and UK usage. One of the first results was this: random-idea-english.blogspot.com/2014/01/… and while it doesn't address that question specifically, it does have an interesting discussion of the history (continued)

of teaching tenses in English. I was actually dismayed to see that the number 12 there wasn't obtained by multiplying 6 tenses * 2 aspects, but instead 3 tenses * 4 aspects -- so even that is not without controversy!

But, the article goes on to describe the origins of the system which I referenced as "standard" in my CP proposal. Quoting from the linked source: "it is perhaps not surprising that many early grammarians went for a six-tense system: there is some variation in terminology, but the actual tenses don't vary. In this system, continuous forms are not counted as tenses, and are usually seen as variations of these six tenses."

And further on: "Another grammarian to develop the three times into six tenses was Lindley Murray. Continuing the Lowthian idea of prescriptive grammar, Murray was the author of English grammar: adapted to the different classes of learners, first published in 1795 and which became probably the most influential grammar book of the first half of the nineteenth century, in both Britain and North America."

The entire subsection under the heading "Six tenses - other grammarians" is particularly informative. So, it appears the 6-tense model I used isn't new or nonstandard, but it is also far from being the universal model taught in schools or to ESL learners. It seems like I shouldn't make this kind of assertion in the CP given the lack of consensus.

But now I'm back to square 1 -- there is no single agreed-on "basic" or "standard" model, and it could be misleading to present any single system as if it were one. But, to give any set of guidelines at all without doing so would require getting into a discussion and comparison of the different possible systems -- which is exactly what @gotube didn't think would be a good idea for this site. (See his comments in the original discussion under the post)